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World War II
Date 25 June 1950 – 4 August 1952
(2 years, 1 month, Expression error: Unexpected < operator. weeks and 3 days)
Place Korean Peninsula, Yellow Sea, Sea of Japan, Korea Strait, China–North Korea border
Result UN victory
  • North Korean invasion of South Korea repelled
  • US-led United Nations invasion of North Korea repelled
  • Chinese and North Korean invasion of South Korea repelled
  • UN counteroffensive push Communist forces out of North Korea
  • North Korea unified with South Korea
Territorial changes Korean Demilitarized Zone established
Belligerents
South Korea

United Nations

North Korea
Commanders and leaders
Rhee Syng-man
Chung Il-kwon
Paik Sun-yup
Shin Sung-mo
United States Harry S. Truman
United States Robert A. Lovett
United States George C. Marshall
United States Douglas MacArthur
United States George S. Patton
United States Matthew Ridgway
United Kingdom Clement Attlee
United Kingdom Winston Churchill
Kim Il-sung
Pak Hon-yong
Choe Yong-gon
Kim Chaek
Mao Zedong
Peng Dehuai
Chen Geng
Deng Hua
Soviet Union Joseph Stalin
Soviet Union Pavel Zhigarev


The Korean War (Korean: 6.25 전쟁, 한국전쟁; Hanja: 韓國戰爭; RR: Yugio Jeonjaeng, Hanguk Jeonjaeng; 25 June 1950 – 4 August 1952) was a war between North Korea (with the support of China and the Soviet Union) and South Korea (with the support of the United Nations, principally from the United States). The war began on 25 June 1950 when North Korea invaded South Korea following clashes along the border and insurrections in the south.

After the surrender of Japan, at the end of World War II, on 15 August 1945, Korea was divided at the 38th parallel into two zones of occupation. The Soviets administered the northern-half and the Americans administered the southern-half. In 1948, as a result of Cold War tensions, the occupation zones became two sovereign states. A socialist state was established in the north under the totalitarian leadership of Kim Il-sung and a capitalist state in the south under the authoritarian leadership of Syngman Rhee. Both governments of the two new Korean states claimed to be the sole legitimate government of all of Korea, and neither accepted the border as permanent.

North Korean military (Korean People's Army, KPA) forces crossed the border and advanced into South Korea on 25 June 1950. The United Nations Security Council denounced the North Korean move as an invasion, and authorized the formation of the United Nations Command and the dispatch of forces to Korea to repel it. These UN decisions were taken without participation of the Soviet Union and the People's Republic of China, both of which supported North Korea. Twenty-one countries of the United Nations eventually contributed to the UN force, with the United States providing around 90% of the military personnel.

After the first two months of war, South Korean Army (ROKA) and the U.S. forces rapidly dispatched to Korea were on the point of defeat. As a result, the ROKA and U.S. troops retreated to a small area behind a defensive line known as the Pusan Perimeter. In September 1950, an amphibious UN counter-offensive was launched at Incheon, and cut off many KPA troops in South Korea. Those who escaped envelopment and capture were forced back north. UN forces invaded North Korea in October 1950 and moved rapidly towards the Yalu River—the border with China—but on 19 October 1950, Chinese forces of the People's Volunteer Army (PVA) crossed the Yalu and entered the war. The surprise Chinese intervention triggered a retreat of UN forces and Chinese forces were in South Korea by late December.

The Korean War was among the most destructive conflicts of the modern era, with approximately 3 million war fatalities and a larger proportional civilian death toll than World War II or the Vietnam War. It incurred the destruction of virtually all of Korea's major cities, thousands of massacres by both sides, including the mass killing of tens of thousands of suspected communists by the South Korean government, and the torture and starvation of prisoners of war by the North Korean command. North Korea became among the most heavily bombed countries in history.

Course of the war

At dawn on Sunday, 25 June 1950, the KPA crossed the 38th Parallel behind artillery fire. The KPA justified its assault with the claim that ROK troops attacked first and that the KPA were aiming to arrest and execute the "bandit traitor Syngman Rhee". Fighting began on the strategic Ongjin Peninsula in the west. There were initial South Korean claims that the 17th Regiment captured the city of Haeju, and this sequence of events has led some scholars to argue that the South Koreans fired first.

Whoever fired the first shots in Ongjin, within an hour, KPA forces attacked all along the 38th Parallel. The KPA had a combined arms force including tanks supported by heavy artillery. The ROK had no tanks, anti-tank weapons or heavy artillery to stop such an attack. In addition, the South Koreans committed their forces in a piecemeal fashion and these were routed in a few days.

On 27 June, Rhee evacuated from Seoul with some of the government. On 28 June, at 2:00 AM, the ROK blew up the Hangang Bridge across the Han River in an attempt to stop the KPA. The bridge was detonated while 4,000 refugees were crossing it and hundreds were killed. Destroying the bridge also trapped many ROK units north of the Han River. Despite such desperate measures, Seoul fell that same day. A number of South Korean National Assemblymen remained in Seoul when it fell, and forty-eight subsequently pledged allegiance to the North.

On 28 June, Rhee ordered the massacre of suspected political opponents in his own country.

In five days, the ROK, which had 95,000 men on 25 June, was down to less than 22,000 men. In early July, when U.S. forces arrived, what was left of the ROK were placed under U.S. operational command of the United Nations Command.

Factors in U.S. intervention

The Truman administration was unprepared for the invasion. Korea was not included in the strategic Asian Defense Perimeter outlined by United States Secretary of State Dean Acheson. Truman himself was at his home in Independence, Missouri. Military strategists were more concerned with the security of Europe against the Soviet Union than East Asia. At the same time, the administration was worried that a war in Korea could quickly widen into another world war should the Chinese or Soviets decide to get involved.

While there was initial hesitance by some in the U.S. government to get involved in the war, considerations about Japan played a part in the ultimate decision to engage on behalf of South Korea. Especially after the fall of China to the Communists, U.S. experts on East Asia saw Japan as the critical counterweight to the Soviet Union and China in the region. While there was no U.S. policy dealing with South Korea directly as a national interest, its proximity to Japan increased the importance of South Korea. Said Kim: "The recognition that the security of Japan required a non-hostile Korea led directly to President Truman's decision to intervene ... The essential point ... is that the American response to the North Korean attack stemmed from considerations of U.S. policy toward Japan."

Another major consideration was the possible Soviet reaction in the event that the U.S. intervened. The Truman administration was fearful that a war in Korea was a diversionary assault that would escalate to a general war in Europe once the United States committed in Korea. At the same time, "[t]here was no suggestion from anyone that the United Nations or the United States could back away from [the conflict]". Yugoslavia—a possible Soviet target because of the Tito-Stalin Split—was vital to the defense of Italy and Greece, and the country was first on the list of the National Security Council's post-North Korea invasion list of "chief danger spots". Truman believed if aggression went unchecked, a chain reaction would be initiated that would marginalize the UN and encourage Communist aggression elsewhere. The UN Security Council approved the use of force to help the South Koreans, and the US immediately began using what air and naval forces that were in the area to that end. The Truman administration still refrained from committing on the ground because some advisers believed the North Koreans could be stopped by air and naval power alone.

The Truman administration was still uncertain if the attack was a ploy by the Soviet Union or just a test of U.S. resolve. The decision to commit ground troops became viable when a communiqué was received on 27 June indicating the Soviet Union would not move against U.S. forces in Korea. The Truman administration now believed it could intervene in Korea without undermining its commitments elsewhere.

United Nations Security Council Resolutions

On 25 June 1950, the United Nations Security Council unanimously condemned the North Korean invasion of South Korea, with UN Security Council Resolution 82. The Soviet Union, a veto-wielding power, had boycotted the Council meetings since January 1950, protesting that the Taiwanese Republic of China and not the mainland People's Republic of China held a permanent seat in the UN Security Council. After debating the matter, the Security Council, on 27 June 1950, published Resolution 83 recommending member states provide military assistance to the Republic of Korea. On 27 June President Truman ordered U.S. air and sea forces to help South Korea. On 4 July the Soviet Deputy Foreign Minister accused the U.S. of starting armed intervention on behalf of South Korea.

The Soviet Union challenged the legitimacy of the war for several reasons. The ROK intelligence upon which Resolution 83 was based came from U.S. Intelligence; North Korea was not invited as a sitting temporary member of the UN, which violated UN Charter Article 32; and the fighting was beyond the UN Charter's scope, because the initial north–south border fighting was classed as a civil war. Because the Soviet Union was boycotting the Security Council at the time, legal scholars posited that deciding upon an action of this type required the unanimous vote of all the five permanent members including the Soviet Union.

Within days of the invasion, masses of ROK soldiers—of dubious loyalty to the Syngman Rhee regime—were retreating southwards or defecting en masse to the northern side, the KPA.

United States' response (July–August 1950)

As soon as word of the attack was received, Acheson informed President Truman that the North Koreans had invaded South Korea. Truman and Acheson discussed a U.S. invasion response and agreed that the U.S. was obligated to act, paralleling the North Korean invasion with Adolf Hitler's aggressions in the 1930s, with the conclusion being that the mistake of appeasement must not be repeated. Several U.S. industries were mobilized to supply materials, labor, capital, production facilities, and other services necessary to support the military objectives of the Korean War. However, President Truman later acknowledged that he believed fighting the invasion was essential to the U.S. goal of the global containment of communism as outlined in the National Security Council Report 68 (NSC 68):

Communism was acting in Korea, just as Hitler, Mussolini and the Japanese had ten, fifteen, and twenty years earlier. I felt certain that if South Korea was allowed to fall, Communist leaders would be emboldened to override nations closer to our own shores. If the Communists were permitted to force their way into the Republic of Korea without opposition from the free world, no small nation would have the courage to resist threat and aggression by stronger Communist neighbors.

In August 1950, the President and the Secretary of State obtained the consent of Congress to appropriate $12 billion for military action in Korea.

Because of the extensive defense cuts and the emphasis placed on building a nuclear bomber force, none of the services were in a position to make a robust response with conventional military strength. General Omar Bradley, Chairman of the Joint Chiefs of Staff, was faced with re-organizing and deploying a U.S. military force that was a shadow of its World War II counterpart.

Acting on Secretary of State Acheson's recommendation, President Truman ordered Supreme Commander for the Allied Powers in Japan General Douglas MacArthur to transfer matériel to the South Korean military while giving air cover to the evacuation of U.S. nationals. The President disagreed with advisers who recommended unilateral U.S. bombing of the North Korean forces, and ordered the U.S. Seventh Fleet to protect the Republic of China (Taiwan), whose government asked to fight in Korea. The United States denied Taiwan's request for combat, lest it provoke a PRC retaliation. Because the United States had sent the Seventh Fleet to "neutralize" the Taiwan Strait, Chinese premier Zhou Enlai criticized both the UN and U.S. initiatives as "armed aggression on Chinese territory".

The drive south and Pusan (July–September 1950)

After the UN Security Council passed Resolution 82, the U.S. government was empowered to select a commander, and the Joint Chiefs of Staff unanimously recommended MacArthur. He therefore became Commander-in-Chief of the UNC, while remaining SCAP in Japan and Commander-in-Chief, Far East. All South Korean forces were also placed under his command. The Eighth U.S. Army (known as the Eight United States Army in Korea, EUSAK), commanded by Major General Walton Walker, was ordered to intervene and drive the invaders back across the 38th parallel, the border between the two countries. With only four lightly equipped and poorly trained divisions, Walker began landing troops on the southeast side of the Korean peninsula in July. The Battle of Osan, the first significant U.S. engagement of the Korean War, involved the 540-soldier Task Force Smith, which was a small forward element of the 24th Infantry Division which had been flown in from Japan. On 5 July 1950, Task Force Smith attacked the KPA at Osan but without weapons capable of destroying the KPA tanks. The KPA defeated the U.S. soldiers; the result was 180 American dead, wounded, or taken prisoner.

After his lead units were virtually destroyed in a few days of furious fighting between Osan and Taejon, Walker realized his assigned mission was impossible and went on the defensive. Pushed steadily back towards the southeast by the North Korean advance, Walker's forces suffered heavy losses and for a time were unable to form a defensible front, even after bringing the 1st Cavalry Division and 25th Infantry Division into the fight. Walker's situation was not helped by MacArthur's unrealistic demands from Tokyo for him not to retreat an inch. Attempting to obey, Walker gave a bombastic "not a step back" speech to his staff and subordinate commanders which did not go over well. The KPA progressed southwards, pushing back U.S. forces at Pyongtaek, Chonan, and Chochiwon, forcing the 24th Division's retreat to Taejon, which the KPA captured in the Battle of Taejon. On 15 July 1950, two days after arrival in Korea, General Walker was mortally wounded when a KPAAF Ilyushin Il-10 strafed his command jeep near the EUSAK headquarters in Daegu, and succumbed to his wounds the following day. Major General William F. Dean of the 24th Division temporarily assumed command. During the fighting the 24th Division suffered 3,602 dead and wounded and 2,962 captured, including General Dean. In an effort to boost morale, General George S. Patton was appointed commander of EUSAK, arriving in Korea on 21 July.

By August, the KPA steadily pushed back the ROK and the Eighth United States Army southwards. The impact of the Truman administration's defense budget cutbacks were now keenly felt, as U.S. troops fought a series of costly rearguard actions. Facing a veteran and well led KPA force, and lacking sufficient anti-tank weapons, artillery or armor, the Americans retreated and the KPA advanced down the Korean Peninsula. During their advance, the KPA purged South Korea's intelligentsia by killing civil servants and intellectuals. On 20 August, General MacArthur warned North Korean leader Kim Il-sung that he would be held responsible for the KPA's atrocities. By September, UN forces were hemmed into a small corner of southeast Korea, near Pusan. This 140 miles (230 km) perimeter enclosed about 10% of Korea, in a line partially defined by the Nakdong River.

Although Kim's early successes led him to predict he would end the war by the end of August, Chinese leaders were more pessimistic. To counter a possible U.S. deployment, Zhou Enlai secured a Soviet commitment to have the Soviet Union support Chinese forces with air cover, and deployed 260,000 soldiers along the Korean border, under the command of Gao Gang. Zhou commanded Chai Chengwen to conduct a topographical survey of Korea, and directed Lei Yingfu, Zhou's military advisor in Korea, to analyze the military situation in Korea. Lei concluded that MacArthur would most likely attempt a landing at Incheon. After conferring with Mao that this would be MacArthur's most likely strategy, Zhou briefed Soviet and North Korean advisers of Lei's findings, and issued orders to PLA commanders deployed on the Korean border to prepare for U.S. naval activity in the Korea Strait.

In the resulting Battle of Pusan Perimeter, the UN forces withstood KPA attacks meant to capture the city at the Naktong Bulge, P'ohang-dong, and Taegu. The United States Air Force (USAF) interrupted KPA logistics with 40 daily ground support sorties that destroyed 32 bridges, halting most daytime road and rail traffic. KPA forces were forced to hide in tunnels by day and move only at night. To deny matériel to the KPA, the USAF destroyed logistics depots, petroleum refineries, and harbors, while the U.S. Navy air forces attacked transport hubs. Consequently, the over-extended KPA could not be supplied throughout the south. On 27 August, 67th Fighter Squadron aircraft mistakenly attacked facilities in Chinese territory and the Soviet Union called the UN Security Council's attention to China's complaint about the incident. The U.S. proposed that a commission of India and Sweden determine what the U.S. should pay in compensation but the Soviets vetoed the U.S. proposal.

Meanwhile, U.S. garrisons in Japan continually dispatched soldiers and matériel to reinforce defenders in the Pusan Perimeter. Tank battalions deployed to Korea directly from the U.S. mainland from the port of San Francisco to the port of Pusan, the largest Korean port. By late August, the Pusan Perimeter had some 500 medium tanks battle-ready. In early September 1950, UN forces outnumbered the KPA 180,000 to 100,000 soldiers.


Battle of Inchon (September 1950)

First Lieutenant Baldomero Lopez of the 1st Battalion, 5th Marines is shown scaling a seawall from a LCVP after landing on Red Beach at Incon, 15 September 1950. Minutes after this photo was taken, Lopez was killed after covering a live grenade with his body while storming a North Korean bunker. He was posthumously awarded the Medal of Honor.

Against the rested and re-armed Pusan Perimeter defenders and their reinforcements, the KPA were undermanned and poorly supplied; unlike the UN forces, they lacked naval and air support. To relieve the Pusan Perimeter, General MacArthur recommended an amphibious landing at Incheon, near Seoul and well over 160 km (100 mi) behind the KPA lines. MacArthur felt that he could turn the tide if he made a decisive troop movement behind KPA lines, and preferred Inchon, over Chumunjin-up or Kunsan as the landing site. Soon after the war began, General MacArthur began planning a landing at Incheon, but the Pentagon opposed him. He had originally envisioned such a landing, code named Operation Bluehearts, for 22 July, with the US Army's 1st Cavalry Division landing at Inchon. However, by 10 July the plan was abandoned as it was clear the 1st Cavalry Division would be needed on the Pusan Perimeter. On 23 July, MacArthur formulated a new plan, code-named Operation Chromite, calling for an amphibious assault by the US Army's 2nd Infantry Division and the United States Marine Corps (USMC)'s 5th Marine Regiment in mid-September 1950. This, too fell through as both units were moved to the Pusan Perimeter. MacArthur decided instead to use the US Army's 7th Infantry Division, his last reserve unit in East Asia, to conduct the operation as soon as it could be raised to wartime strength.

On 23 August MacArthur briefed his plans to Chief of Staff of the United States Army General Joseph Lawton Collins, Chief of Naval Operations Admiral Forrest Sherman, and United States Air Force (USAF) operations deputy Lieutenant General Idwal H. Edward. He said that, because it was so heavily defended, the North Koreans would not expect an attack there, that victory at Inchon would avoid a brutal winter campaign, and that, by invading a northern strong point, UN forces could cut off KPA lines of supply and communication. Sherman and Collins returned to Washington, D.C., and reported back to Secretary of Defense Louis A. Johnson. The Joint Chiefs of Staff approved MacArthur's plan on 28 August. President Truman also provided his approval.

When authorized, he activated a combined U.S. Army and Marine Corps, and ROK force. US X Corps, led by Major General Edward Almond, consisted of 40,000 men of the 1st Marine Division, the 7th Infantry Division and around 8,600 ROK soldiers. Before the main land battle, UN forces landed spies in Inchon and bombarded the city's defenses via air and sea. Deception operations were also carried out to draw North Korean attention away from Inchon. While both Kim Il-Sung and Kim Chaek were aware of the likelihood of an American amphibious landing at Inchon, they decided to stake everything on the Second Battle of the Naktong Bulge and left Inchon lightly defended.

At 06:33 on 15 September 1950, the lead amphibious assault force of X Corps hit "Green Beach" on the northern side of Wolmido. MacArthur was personally present aboard the flagship of the amphibious assault force, USS Mount McKinley. Landings followed at Red Beach and Blue Beach, 2.5 miles (4.0 km) southeast of Red and Green beaches, at the next tidal window at 05:30 PM. The Marines clambered over the sea wall and through enemy bunkers to capture the dominating ground surrounding the beachhead. X Corps faced few KPA defenders at Incheon: military intelligence, psychological warfare, guerrilla reconnaissance, and protracted bombardment facilitated a relatively light battle. However, the bombardment destroyed most of the city of Incheon. By morning they had pressed 10 km inland and controlled the Inchon-Seoul supply route.

The North Koreans retreated to Seoul, as Major General Oliver P. Smith, the commander of the 1st Marine Division, planned a two-pronged attack to take Seoul from the north and southwest. In contrast to the quick victory at Inchon, the advance on Seoul was slow and bloody. Just before dawn on 17 September, two companies of the 5th Marines, supported by artillery and M-26 tanks, defeated a counterattack by a column of six T-34 tanks near Blue Beach. By the morning of 18 September, 2nd Battalion, 5th Marines had captured Kimpo Airfield, the largest and most important in Korea. The KPA launched another T-34 attack, which was trapped and destroyed and a Yak bombing run in Inchon harbor, which did little damage. The KPA attempted to stall the UN offensive to allow time to reinforce Seoul and withdraw troops from the south. Though warned that the process of taking Seoul would allow remaining KPA forces in the south to escape, MacArthur felt that he was bound to honor promises given to the South Korean government to retake the capital as soon as possible. In an enormous hurry to capture Seoul, Almond threw the 7th Infantry Division's 32nd Regiment into the attack from the southeast. The fighting for Soeul was ferocious, and casualties mounted as the forces engaged in house-to-house fighting. UN artillery fire and close air support struck the city heavily, and napalm caused incendiary fires. Many civilians died while KPA forces fought fanatically. Almond declared Seoul liberated the evening of 25 September, a claim repeated by MacArthur the following day. However, at the time of Almond's declaration, U.S. Marines were still engaged in house-to-house combat as the KPA remained in most of the city. It was not until 27 September that the last of the KPA elements were driven out or destroyed abd the U.S. and UN flags were raised over the capitol.

The Inchon operation was later described as MacArthur's "greatest success" and a strategic masterpiece, but it was followed by an advance to Seoul in ground battle so slow and measured that it constituted an operational disaster, largely negating the successful landing. MacArthur was also furious with Patton, who instead of a coordinated attack had launched his breakout offensive a week earlier. As Patton had bypassed Inchon, there were discussions that the whole operation had been made redundant. Only by that point, cancelling it altogether would have forced MacArthur to explain himself to the Joint Chiefs of Staff, merely three weeks after claiming it was the only way to defeat the KPA.

Patton's breakout offensive from the Pusan Perimeter (September 1950)

On 9 September Patton's Eighth Army began its breakout from the Pusan Perimeter. While the attack had been originally scheduled to begin a week later, one day after the Inchon landings, Patton took the initiative and moved up the offensive. Patton's strategy of his advance through France in 1944. Eighth Army typically employed forward scout units to determine enemy strength and positions. Self-propelled artillery moved with the spearhead units and was sited well forward, ready to engage protected KPA positions with indirect fire. The speed of the advance forced Patton's units to rely heavily on air reconnaissance and tactical air support. Once located, the armored infantry would attack using tanks as infantry support. Other armored units would then break through enemy lines and exploit any subsequent breach, constantly pressuring withdrawing KPA forces to prevent them from regrouping and reforming a cohesive defensive line.

Task Force Lynch, 3rd Battalion, 7th Cavalry Regiment, and two 70th Tank Battalion units (Charlie Company and the Intelligence–Reconnaissance Platoon) advanced through 171.2 km (106.4 mi) of KPA territory to reach the Han River near Punwon-ni on 17 September. After two days of heavy fighting I Corps forces had crossed the river. Meanwhile, Eighth Army forces joined with the 7th Infantry Division at Ansan on 18 September. While X Corps engaged the KPA defenders in and around Seoul, Patton's Eighth Army launched a wide-scale counteroffensive. 2nd Infantry Division encircled Seoul from the north, while the 24th Infantry Division held the Han River. The rest of the Army was ordered to advance on the 38th parallel. UN and ROK forces advanced rapidly, threatening to trap the main KPA force in Southern Korea. U.S. air raids caused heavy damage to the KPA, destroying most of its tanks and much of its artillery. KPA troops in the south, instead of effectively withdrawing north, rapidly disintegrated, leaving Pyongyang vulnerable. During the general retreat only 25,000 to 30,000 KPA soldiers managed to reach the KPA lines. U.S. forces reached a point only 5 miles (8.0 km) below the 38th Parallel on 22 September.

On 18 September, Stalin dispatched General H. M. Zakharov to North Korea to advise Kim Il-sung to halt his offensive around the Pusan perimeter and to redeploy his forces to defend Seoul. Chinese commanders were not briefed on North Korean troop numbers or operational plans. As the overall commander of Chinese forces, Zhou Enlai suggested that the North Koreans should attempt to eliminate the UN forces at Incheon only if they had reserves of at least 100,000 men; otherwise, he advised the North Koreans to withdraw their forces north. On 27 September, Stalin convened an emergency session of the Politburo, in which he condemned the incompetence of the KPA command and held Soviet military advisers responsible for the defeat.

UN forces invade North Korea (September–October 1950)

On 27 September, MacArthur received the top secret National Security Council Memorandum 81/1 from Truman reminding him that operations north of the 38th Parallel were authorized only if "at the time of such operation there was no entry into North Korea by major Soviet or Chinese Communist forces, no announcements of intended entry, nor a threat to counter our operations militarily". On 29 September MacArthur restored the government of the Republic of Korea under Syngman Rhee. On 30 September, US Defense Secretary George Marshall sent an eyes-only message to MacArthur: "We want you to feel unhampered tactically and strategically to proceed north of the 38th parallel." During October, the South Korean police executed people who were suspected to be sympathetic to North Korea, and similar massacres were carried out until early 1951. The Joint Chiefs of Staff on 27 September sent to General MacArthur a comprehensive directive to govern his future actions: the directive stated that the primary goal was the destruction of the KPA, with unification of the Korean Peninsula under Rhee as a secondary objective "if possible"; the Joint Chiefs added that this objective was dependent on whether or not the Chinese and Soviets would intervene, and was subject to changing conditions.

On 30 September, Zhou Enlai warned the US that China was prepared to intervene in Korea if the US crossed the 38th Parallel. Zhou attempted to advise KPA commanders on how to conduct a general withdrawal by using the same tactics that allowed Chinese communist forces to successfully escape Chiang Kai-shek's Encirclement Campaigns in the 1930s, but by some accounts KPA commanders did not use these tactics effectively. Historian Bruce Cumings argues, however, that the KPA's rapid withdrawal was strategic, with troops melting into the mountains from where they could launch guerrilla raids on the UN forces spread out on the coasts.

By 1 October 1950, the UN Command repelled the KPA northwards past the 38th Parallel; the ROK advanced after them, into North Korea. MacArthur made a statement demanding the KPA's unconditional surrender. Six days later, on 7 October, with UN authorization, the UN Command forces followed the ROK forces northwards.

The US Eighth Army, led by Patton, drove up western Korea and captured Pyongyang on 4 October 1950, while ROK forces captured Wonsan on 5 October. On 11 October ROK forces captured the port of Hungnam. The 101st Airborne Division staged a parachute assault on 6 October 1950 at Sunchon and Sukchon. Their objectives were cutting off KPA forces retreating ahead of the US Eighth Army general advance from the south, capturing important North Korean government officials evacuating Pyongyang, and liberating US prisoners of war (POWs) being moved out of Pyongyang. After five days of heavy fighting the 27th British Commonwealth Brigade reached Sunchon–Sukchon and relieved the US paratroopers. Premier Kim Il Sung's government and most important officials had already moved to Kanggye in the mountains 20 miles (32 km) southeast of Manpojin on the Yalu River, and most of the American POWs had been moved to more remote parts of North Korea and were unable to be rescued. However, the operation had succeded in destroying most of the remnants of the KPA.

At month's end, UN forces had reached a line running from Sukchon in the west to Kowon in the east, which was subsequently dubbed the Walker Line. The UN forces held 135,000 KPA prisoners of war. As they neared the Sino-Korean border, the UN forces in the west were divided from those in the east by 50–100 miles (80–161 km) of mountainous terrain. In addition to the 145,000 captured, the KPA had also suffered some 200,000 men killed or wounded for a total of 345,000 casualties since the end of June 1950, and had lost 313 tanks (mostly T-34/85 models). A mere 15,000 KPA regulars retreated across the 38th Parallel, as their military had entirely collapsed. The UN forces on the peninsula numbered 259,722 combat troops (including 155,126 Americans and 82,786 South Koreans), 119,559 rear area troops, and 36,667 US Air Force personnel.

On 20 October General MacArthur, based on the Joint Chiefs of Staff directive of 18 October, restrained in his UNC Operations Order 4 UN ground forces other than ROK troops from operating north of a line extending along the Chongchon River from in the West through Hungnam in the East. In the policy laid down in this directive, only ROK forces were to be used in the provinces of Korea bordering on the Yalu River. While awaiting orders to continue the advance, UN forces strengthened the Walker Line. Taking advantage of the UN Command's strategic momentum against the communists, MacArthur believed it necessary to extend the Korean War into China to destroy depots supplying the North Korean war effort. Truman disagreed, and ordered caution at the Sino-Korean border.

ROK advance to the Yalu (October 1950)

While UN ground forces were restricted from advancing north of the Walker Line, ROK forces pressed forward to the Yalu River — to the extreme northern limits of the country. The ROK 6th Division of ROK II Corps met no serious opposition and traveling fast up the valley of the Ch'ongch'on, it reached Huich'on the night of 23 October. There it left the valley of the Ch'ongch'on and turned west, the 7th Regiment leading. Its advanced battalion marched northwest over a cart trail, but the remainder of the regiment had to turn west from Huich'on on a road to Onjong.

The night of 24–25 October, the 7th Regiment passed through Onjong, then turned north and joined its advanced battalion. Finding the road clear, it headed north for its objective, the town of Ch'osan, 80 km (50 mi) away on the Yalu. The Reconnaissance Platoon from the 7th Regiment, ROK 6th Division, was the first UN unit to reach the northern border of North Korea, and, as events turned out, it was the only element operating under Eighth Army command ever to get there during the war. Following behind the 6th Division, the ROK 8th Division had reached the valley of the Ch'ongch'on at Kujangdong the night of 25–26 October, marching from Sunch'on through Tokch'on. On the 26th, the day the advanced elements of the 6th Division reached the Yalu, the 8th turned up the Ch'ongch'on Valley toward Huich'on for the purpose of joining the 6th Division.

China intervenes (October–November 1950)

On 30 June 1950, five days after the outbreak of the war, Zhou Enlai, premier of the PRC and vice-chairman of the Central Military Committee of the CCP (CMCC), decided to send a group of Chinese military intelligence personnel to North Korea to establish better communications with Kim II Sung as well as to collect first-hand materials on the fighting. One week later, on 7 July, Zhou and Mao chaired a conference discussing military preparations for the Korean Conflict. Another conference took place on 10 July. Here it was decided that the Thirteenth Army Corps under the Fourth Field Army of the PLA, one of the best trained and equipped units in China, would be immediately transformed into the Northeastern Border Defense Army (NEBDA) to prepare for "an intervention in the Korean War if necessary". On 13 July the CMCC formally issued the order to establish the NEBDA, appointing Deng Hua, the commander of the Fifteenth Army Corps and one of the most talented commanders of the Chinese Civil War, to coordinate all preparation efforts.

On 20 August 1950, Premier Zhou Enlai informed the UN that "Korea is China's neighbor... The Chinese people cannot but be concerned about a solution of the Korean question". Thus, through neutral-country diplomats, China warned that in safeguarding Chinese national security, they would intervene against the UN Command in Korea. President Truman interpreted the communication as "a bald attempt to blackmail the UN", and dismissed it. Mao ordered that his troops should be ready for action by the end of August. Stalin, by contrast, was reluctant to escalate the war with a Chinese intervention.

On 1 October 1950, the day that UN troops crossed the 38th Parallel, the Soviet ambassador forwarded a telegram from Stalin to Mao and Zhou requesting that China send five to six divisions into Korea, and Kim Il-sung sent frantic appeals to Mao for Chinese military intervention. At the same time, Stalin made it clear that Soviet forces themselves would not directly intervene.

In a series of emergency meetings that lasted from 2 to 5 October, Chinese leaders debated whether to send Chinese troops into Korea. There was considerable resistance among many leaders, including senior military leaders, to confronting the US in Korea. Mao strongly supported intervention, and Zhou was one of the few Chinese leaders who firmly supported him. After Lin Biao politely refused Mao's offer to command Chinese forces in Korea (citing his upcoming medical treatment), Mao decided that Peng Dehuai would be the commander of the Chinese forces in Korea after Peng agreed to support Mao's position. Mao then asked Peng to speak in favor of intervention to the rest of the Chinese leaders. After Peng made the case that if US troops conquered Korea and reached the Yalu they might cross it and invade China, the Politburo agreed to intervene in Korea. On 4 August 1950, with a planned invasion of Taiwan aborted due to the heavy US naval presence, Mao reported to the Politburo that he would intervene in Korea when the People's Liberation Army's (PLA) Taiwan invasion force was reorganized into the PLA North East Frontier Force. On 8 October 1950, Mao redesignated the PLA North East Frontier Force as the People's Volunteer Army (PVA).

To enlist Stalin's support, Zhou and a Chinese delegation arrived in Moscow on 10 October, at which point they flew to Stalin's home on the Black Sea. There they conferred with the top Soviet leadership, which included Joseph Stalin as well as Vyacheslav Molotov, Lavrentiy Beria and Georgy Malenkov. Stalin initially agreed to send military equipment and ammunition, but warned Zhou that the Soviet Air Force would need two or three months to prepare any operations. In a subsequent meeting, Stalin told Zhou that he would only provide China with equipment on a credit basis, and that the Soviet Air Force would only operate over Chinese airspace, and only after an undisclosed period of time. Stalin did not agree to send either military equipment or air support until March 1951. Mao did not find Soviet air support especially useful, as the fighting was going to take place on the south side of the Yalu. Soviet shipments of matériel, when they did arrive, were limited to small quantities of trucks, grenades, machine guns, and the like.

Immediately on his return to Beijing on 18 October 1950, Zhou met with Mao Zedong, Peng Dehuai and Gao Gang, and the group ordered two hundred thousand PVA troops to enter North Korea, which they did on 19 October. UN aerial reconnaissance had difficulty sighting PVA units in daytime, because their march and bivouac discipline minimized aerial detection. The PVA marched "dark-to-dark" (19:00–03:00), and aerial camouflage (concealing soldiers, pack animals, and equipment) was deployed by 05:30. Meanwhile, daylight advance parties scouted for the next bivouac site. During daylight activity or marching, soldiers were to remain motionless if an aircraft appeared, until it flew away; PVA officers were under order to shoot security violators. Such battlefield discipline allowed a three-division army to march the 460 km (286 mi) from An-tung, Manchuria, to the combat zone in some 19 days. Another division night-marched a circuitous mountain route, averaging 29 km (18 mi) daily for 18 days.

Meanwhile, on 15 October 1950, President Truman and General MacArthur met at Wake Island. This meeting was much publicized because of the General's discourteous refusal to meet the President on the continental United States. To President Truman, MacArthur speculated there was little risk of Chinese intervention in Korea, and that the PRC's opportunity for aiding the KPA had lapsed. He believed the PRC had some 300,000 soldiers in Manchuria, and some 100,000–125,000 soldiers at the Yalu River. He further concluded that, although half of those forces might cross south, "if the Chinese tried to get down to Pyongyang, there would be the greatest slaughter" without air force protection.

After secretly crossing the Yalu River on 19 October, the PVA 13th Army Group launched the First Phase Offensive on 25 October, attacking the advancing ROK forces near the Sino-Korean border. This military decision made solely by China changed the attitude of the Soviet Union. Twelve days after PVA troops entered the war, Stalin allowed the Soviet Air Force to provide air cover, and supported more aid to China. After inflicting heavy losses on the ROK II Corps at the Battle of Onjong and Unsan, the ROK forces retreated back to the Chongchon River, while the PVA unexpectedly disappeared into mountain hideouts following victory. It is unclear why the Chinese did not press the attack and follow up their victory. By 6 November, however, logistics difficulties had forced the Chinese to end the First Phase Campaign and their forces were observed withdrawing northwards. On 13 November, Mao appointed Zhou Enlai the overall commander and coordinator of the war effort, with Peng as field commander.

Offensive preparations (November 1950)

Despite the success of the PVA First Phase Campaign, the UN planners still believed that China had not intervened in Korea on a large scale. The suddenness of the PVA withdrawal in the face of a victory further reinforced this belief. Working on the assumption that only 30,000 PVA troops could remain hidden in the hills, General Douglas MacArthur ordered the bombing of the bridges over the Yalu River in an effort to cut off PVA reinforcements. Confident that the UN air forces could detect and disrupt any troop movements across the Yalu River, General MacArthur issued on 8 November an order to his ground commanders in Korea which changed all earlier orders drastically. He now removed all restrictions on the use of UN ground forces north of the Walker Line, and instructed his commanders to press forward to the northern limits of Korea along the Yalu River, utilizing all their forces, and destroy the Chinese forces in Korea as well as the remaining North Koreans. MacArthur aid the defeat of the North Koreans had been decisive when the Chinese intervened in "one of the most offensive acts of international lawlessness of historic record." General MacArthur announced his future intentions: "Our present mission is limited to the destruction of those forces now arrayed against us in North Korea with a view to achieving the United Nations' objective to bring unity and peace to the Korean nation and its people."

Unknown to the UN planners, however, there were already 180,000 PVA troops stationed in Korea, with more reinforcements infiltrating across the border. Although the PVA was ordered to maintain a defensive posture in North Korea until Soviet weapons could arrive in the spring of 1951, its earlier successes convinced the Chinese leadership that the PVA was capable of turning the tide of UN advance. Encouraged by the fact that the UN did not know their true numbers, PVA Commander Peng Dehuai outlined the Second Phase Campaign, a counteroffensive aimed at pushing the UN forces back to a line halfway between Ch'ongch'on River and Pyongyang. As a part of a deception plan to further reinforce the weak appearance of PVA forces, Peng ordered all units to rapidly retreat north while releasing POWs along the way. With 230,000 troops at his disposal and another 150,000 heading to the Chosin Reservoir, Peng authorized the start of the Second Phase Campaign on 22 November 1950.

While MacArthur was unconvinced that the Chinese had openly intervened because of the sudden PVA withdrawal, Patton was convinced the PVA was waiting in ambush. Patton and his staff therefore issued on 10 November the operation plan for Eighth Army's offensive which did not envision a full-scale advance on the Yalu River. Instead, the plan called for a reconnaissance-in-force disguised as an offensive north of the Chongchon River, which would draw the PVA forces out and launch their counteroffensive. Should enemy pressure be too great the forces would retreat behind the Walker Line. When the Chinese had depleted their supplies and overextended their supply lines, the Eight Army would launch a general offensive with the US I Corps to the west, US IX Corps in the center and the reconstituted ROK II Corps to the east. On the eastern side of the peninsula, the X Corps would advance towards Hungnam and then northwards towards the Chosin Reservoir. The US 3rd Infantry Division, in reserve, would deal with any possible PVA infiltrations. Patton, having commanded the US Third Army during the Ardennes Offensive in World War II, had requested that the Eight Army to be equipped with winter clothing for the upcoming offensive.

Meanwhile, the PVA 13th Army was hiding in the mountains with the 50th and 66th Corps to the west, the 39th and the 40th Corps in the center and the 38th and 42nd Corps to the east. Anticipating the UN advances, the PVA planned a series of counterattacks to catch the UN forces off guard. Hoping to repeat the success of the earlier First Phase Campaign, the 38th and 42nd Corps would first attack ROK II Corps and destroy the UN right flank, then cut behind the UN lines. At the same time, the 39th and 40th Corps would hold UN forces in place while preventing any reinforcements to ROK II Corps. The 50th and 66th Corps would stay behind and check the advances on the UN left flank.

Although the PVA 13th Army had a nominal strength of 230,000 men, its actual strength during the battle could be as low as 150,000 men. The PVA 66th Corps, for example, had only 6,600 men per division at the start of the battle, as opposed to the expected 10,000 men per division. There was also only one firearm available for every three soldiers, and the rest were employed as grenade throwers. Because most of the Chinese howitzers and guns were left behind in Manchuria, mortars were the only artillery support available for the PVA. For the counteroffensive, the average soldier was issued with only five days worth of rations and ammunition, and resupply could only be obtained by scavenging on the battlefield. To compensate for its shortcomings, the PVA relied extensively on night attacks and infiltrations in order to avoid the UN firepower. The primitive logistics system had also allowed the PVA to maneuver over the rough hilly terrains, thus enabled them to by-pass the UN defenses and to surround the isolated UN positions. Because the Chinese had captured large numbers of Nationalist weapons during the Chinese Civil War, most of the PVA weapons were composed of US-made small arms such as the Thompson submachine gun, the M1 Garand rifle, the M1918 Browning Automatic Rifle, the bazooka and the M2 mortar.

Home-by-Christmas, Second and Third Phase Offensives (November–December 1950)

Acting on MacArthur's instructions, Patton launched the Home-by-Christmas Offensive at 10:00 on 22 November 1950. With the ROK II Corps placed on the Eighth Army's right flank, the advance was led by the US 24th Infantry Division of I Corps, the US 25th Division of the IX Corps, and the 1st Marine Division of the X Corps. The four UN Corps advanced cautiously in a continuous front line in order to prevent more ambushes similar to the PVA First Phase Campaign. Except for the strong PVA resistance against ROK II Corps, the Eighth Army met little opposition, and the line between Chongju to Yongwon was occupied on the night of the 25 November.

As the US Eighth Army stopped its advance on the afternoon of 25 November 1950, the PVA 13th Army commenced the Second Phase Campaign. A massive frontal attack was launched against the entire UN line from Yongsan-dong to Yongdong-ni. To the west, the ROK 1st Infantry Division of US I Corps was attacked by the PVA 66th Corps at Yongsan-dong. In the center, strong probing actions by the PVA 39th and 40th Corps were carried out against US IX Corps at Ipsok and Kujang-dong. In the east, the PVA 38th and 42nd Corps broke through ROK II Corps' line at Tokchon and Yongdong-ni. Realizing the threat to his right flank, Patton ordered the Eight Army to fight a tactical withdrawal across the Ch'ongch'on River towards the Walker Line running through Sukchon – Sunchon – Sinchang-ni. As the ROK II Corps was facing collapse on 27 November, Peng immediately ordered the PVA 38th Corps to cut the road between Kunu-ri and Sunchon in the US IX Corps rear, while the PVA 42nd Corps would surround the entire Eighth Army by rushing south through Pukchang-ni and capture Sunchon. At the same day, Patton ordered the the US 1st Cavalry Division and the Anglo-Australian 27th Commonwealth Infantry Brigade to secure the right flank. The US 1st Cavalry Division would contain the PVA breakthrough at Pukchang-ni, while the 27th Commonwealth Brigade secured the road between Kunu-ri.

Chinese forces, however, had infiltrated the roads between Kunu-ri and Sunchon and constructed roadblocks which delayed the withdrawal of the US 25th Infantry Division. As the 2nd Infantry Division entered the valley, later known as the "Gauntlet", the PVA machine guns delivered punishing fire while mortar shells saturated the road. The length of the roadblock caught the 25th Infantry Division by surprise, and the road was soon filled with wrecked vehicles and wounded and dead soldiers. During the day, the air cover tried to suppress the PVA positions with some success, but with no air cover at night, the PVA attack intensified. The last stragglers from the US 25th Infantry Division finally arrived at Sunchon on 1 December. To the east, the Chinese marched south of the Chosin Reservoir and attacked the UN forces northwest of Hamhung. The 1st Marines, having formed a defensive line through Chagaedung – Yonggwang – Sinhung, stalled the PVA offensive in order to facilitate the withdrawal of the ROK 3rd and Capital Infantry Divisions. They demolished bridges and cratered the road behind them. By 2 December the UN and ROK forces had withdrawn to Kumya and the Ryonghŭng River.

The attacks had caught UN planners and troops by surprise, and in the aftermath of the withdrawal, US Eighth Army's casualty number exceeded 5,000, while ROK formations had suffered 20,000 casualties. However, the majority of the UN forces were intact along the Walker Line. As the UN forces were regrouping, Patton constantly toured the front lines. He whipped his officers into shape, and made it clear he expected the Army to get out of their jeeps and start toughening up. Patton emphasized the UN forces took advantage of ground and aerial reconnaissance, the terrain, artillery, stronger defensive positions, and more flares to illuminate the sky during night fighting. Patton managed to revive the esprit de corps of the bloodied Eighth Army immediately began to revive. On the other hand, the PVA were beginning to outrun its logistics capability as food, ammunition, and matériel were carried nightly, on foot and bicycle, from the border at the Yalu River to the frontline.

After having regrouped following the battle of the Ch'ongch'on River, the PVA launched the Third Phase Offensive in the evening of 8 December against the UN and ROK forces along the Walker Line, which saw some of the most brutal fights of the Korean War. The five-prong offensive led to heavy fighting around Sukchon, Sunchon, Chamo-ri, Unsan, Sinchang-ni, Yonghung, Ryongwon-ri, Munha-ri and Kumya. Utilizing night attacks in which UN fighting positions were encircled and then assaulted by numerically superior troops who had the element of surprise, the PVA attacks were accompanied by loud trumpets and gongs, which fulfilled the double purpose of facilitating tactical communication and mentally disorienting the enemy. UN forces initially had no familiarity with this tactic, and as a result, some soldiers panicked. The PVA made appreciable gains and forced the UN troops along the Walker Line to form a thin line of defense, relying on mobile reserves for the strength to push back PVA attackers. On 14–15 December the situation was so dire for the UN troops that the Eighth Army and ROK moved their headquarters elements from Sunchon to Pyongyang to prevent them from being overrun, though Patton remained in Sunchon with a small forward detachment. They also prepared their logistics systems for a retreat to a smaller defensive perimeter called the Kansas Line. The battle of Sunchon is sometimes known as the "Gettysburg of the Korean War": 5,600 South Korean, U.S., and French troops were cut off and surrounded on all sides by 25,000 PVA. The US 2nd Infantry Division's 23rd Regimental Combat Team, the French Battalion and ROK units successfully held off the numerically superior PVA forces for two days until relieved. By 16 December however, Patton decided another retreat would not be necessary.

The reversal of fortunes in the Korea War was a shock to the military and political leaders of the United States. The US contemplated that it might have to withdraw its military forces from Korea. Immediately given up was the idea that the two Koreas could be united into a single pro-US/UN country. On 11 December 1950 the military situation for the US in Korea looked so grim that the US voted for a UN ceasefire resolution that would have been very favorable to the PVA. The proposal suggested an immediate implementation of a ceasefire, withdrawal of foreign military forces in stages, and a meeting with the participation of the United Kingdom, the US, the Soviet Union, and Communist China would be arranged to resolve problems in the Far East, among which would be the problems of the status of Taiwan and the representation of China in the UN. The proposal was rejected by the Chinese government which was convinced of the PVA's invincibility, and also wanted to demonstrate China's desire for a total victory through the expulsion of the UN forces from Korea. Following the failure of ceasefire negotiations in December and the failure of the PVA to break through the Walker Line, the United Nations General Assembly passed Resolution 498 on 1 January, condemning the PRC as an aggressor, and called upon its forces to withdraw from Korea.

By 20 December the Third Phase Offensive had ground to a halt, and the PVA was suffering from logistics problems and exhaustion after their earlier victories. Casualty ratios were grievously disproportionate; Peng had expected a 1–1 or 2-1 ratio, but instead, Chinese combat casualties from 8 to 20 December totaled between 40,000 and 80,000 compared to only 8,000 for the UN – a casualty ratio between 5–1 and 10–1. By the time Peng had called off the attack in the western sector on 29 April, the three participating armies had lost a third of their front-line combat strength within a week. Additional casualties were incurred on 30 April. On 15 May 1951, the PVA commenced th Arguing against the planned Fourth Phase Campaign, PVA Commander Peng Dehuai telegraphed to Mao that the PVA would need at least three months to replace its casualties, while most of its troops were in critical need of resupply, rest and reorganization. The PVA were now suffering from hunger and the lack of winter clothing. PVA Deputy Commander Han Xianchu later reported to Peng that poor logistics and the exhaustion had cost the "backbone" of the Chinese forces during the Third Phase Campaign. US Far East Air Forces' "Interdiction Campaign No.4 ", which was launched on 12 December 1950 against PVA/KPA supply lines, also made the PVA unable to sustain any further offensives southward. Believing that the UN forces were thoroughly demoralized and unable to counterattack, Mao finally permitted the PVA to rest for at least two to three months, while Peng and other Chinese commanders were planning for a decisive battle in the spring of 1951. To the surprise of Chinese commanders, Patton and the Eighth Army soon counterattacked the PVA with Operation Thunderbolt on 5 January 1951.

UN counteroffensives (January–February 1951)

Following their failure of the Third Phase Offensive (8–20 December), it became apparent that the PVA/KPA forces were withdrawing from the Walker Line. The withdrawal fit the pattern of PVA/KPA operations observed before, in which assault forces were obliged to pause for refitting after a week or so of battle. During the evening of 22 December General Patton planned an advance designed to deny the PVA/KPA any respite in which to prepare new attacks and, in particular, designed to destroy those enemy forces located between the Walker Line and the Ch'ongch'on River. He intended that two principal thrusts by UN forces, up the road from Sukchon beyond Anju and up the road from Unsan beyond Kaech'ŏn, would block the main paths of PVA/KPA withdrawal. The 11th Airborne Division would land near Anju and Kaech'ŏn and seize the bridges over the Ch'ongch'on River. Other forces were to move through and clear the adjacent ground. The offensive was named Operation Thunderbolt.

General Patton instructed US I and IX Corps to destroy PVA/KPA forces located between the Taedon and Ch'ongch'on River south of a line, designated Idaho, running Ch'ongch'on northeastward between Anju and Tokchon, an advance of approximately 20–40 km above the front line. Two armored task forces would attack to the north through Anju and and Kaech'ŏn, with Task Force Johnson of I Corps linking up with the 187th east of Anju and Task Force Dog of IX Corps linking up with north of Kaech'ŏn, trapping the NKPA between the two forces. The ROK 1st Infantry Division and US 2nd, 24th and 25th Infantry Divisions would follow the armored task forces. To the east, X Corps would march on Hamhung, and approximately advance of 40 km. In terms of ground to be gained and held, however, Patton intended that this carry his forces no farther than the lower bank of the Ch'ongch'on in the west and a general line extending eastward from the Ch'ongch'on River through Hamhung on the coast. Only if PVA/KPA forces elected to withdraw above the Ch'ongch'on would he consider occupying a defense line farther north, and in this context he asked his staff near for recommendations on the most advantageous terrain lines for the Eighth Army to occupy during the winter and spring months.

Operation Thunderbolt commended at 05:45 on 5 January and was preceded by the largest artillery bombardment of the Korean War. The PVA/KPA forces were taken by surprise, as the opening phase of operation gave promise that the Eighth Army might reach its final ground objectives almost by default. Employing only a delaying action by small forces, the PVA/KPA line units frequently offered stubborn resistance, including local counterattacks, but more frequently opposed approaching Eighth Army forces at long range, then withdrew. Helped by good close air support after daybreak, the assault battalions pushed through moderate resistance, much of it in the form of small arms, machine gun, and mortar fire and a profusion of well placed antitank and antipersonnel mines, for first-day gains of 2–4 km. Meanwhile, to the east the 1st Marine Division of the X Corps advanced steadily, facing only limited resistance as they reached reaching Hamhung by 11 January.

Patton kept a careful watch over the operation, reconnoitering much of the zone of advance from the air and questioning Corps' commanders closely during the first three days of the operation on the problems weather had created. Frequent airdrops kept the supply problem from becoming critical, and by 25 January engineers had repaired much of the damage to main lines of communication. The advance continued, if far more slowly than anticipated.

To the north, the 11th Airborne Division faced the toughest resistance. After the US Rangers had secured the three dropzones at 08:00, the 187th Paracute Infantry Regiment landed at Maengjungni, 9 km northwest of Anju, the 511th Parachute Infantry Regiment landed south of Anju, while the 188th Parachute Infantry Regiment landed 5 km north of Kaech'ŏn. The 187th made a model crossing of the Taeryong and Ch'ongch'on Rivers, the regiment reached the northern shore almost unopposed and captured the bridges. The PVA/KPA forces, realizing the 11th Airborne Division threatened them with encirclement, launched night attacks with small arms, machine gun, and mortar fire. A brutal five-day battle in freezing weather soon followed, 8,000 men were encircled and attacked by about 60,000 Chinese troops. The UN forces were nevertheless able to hold the bridges over the Taeryong and Ch'ongch'on, inflicting heavy casualties on the Chinese.

On 11 January, Task Force Johnson linked up with the 187th Infantry Regiment at Sinanju, and crossed the Ch'ongch'on. Advancing steadily against light to moderate resistance, all but the ROK 6th Infantry Division, which the cavalrymen and Marines on either side gradually pinched out, were on the Idaho Line by dark on 13 January. By 18 January and had led to the complete destruction of the 50th and 66th PVA Armies. Patton's ability to advance rapidly and encircle two PVA armies during the middle of winter was one of his most remarkable achievements during the war.

Patton's strategy with his army favored speed and aggressive offensive action, and as such, he notified General MacArthur on 17 January that the Eight Army would continue its advance to the Yalu River, with the objective being the destruction of enemy troops and materiel. However, the gains he already had registered in Operation Thunderbolt had influenced a decision in Washington by which operations above the Ch'ongch'on River assumed new importance as a political question. The decision centered on how and when to approach an desired cease-fire. Notwithstanding the building evidence of KPA offensive preparations, officials of the Departments of State and Defense believed that Patton's recent successes might have convinced the Chinese and North Koreans that they could not win a military victory and, if this was the case, that they might agree to negotiate an end to hostilities. On the advice of these officials, President Harry S. Truman planned to make a public statement suggesting the United Nations' willingness to end the fighting. The statement was carefully worded to avoid a threatening tone and so to encourage a favorable reply. Truman intended to deliver the appeal as soon as his statement had been approved by officials of all nations that had contributed forces to the UN Command.

The timing of the presidential announcement was tied also to the fact that Patton's forces had reached the Ch'ongch'on. The consensus in Washington was that the Chinese would be more inclined to agree to a cease-fire under conditions which reunited Korea while establishing a demilitarized zone on the Sino-Korean border and gave the People's Republic of China the seat in the UN Security Council still controlled by the Republic of China. Therefore, while there was no intention to forbid all ground action above the Ch'ongch'on, there was some question in the mind of Secretary of State Dean Acheson and among many members of the United Nations whether the Eighth Army should make a general advance towards the Yalu.

The Joint Chiefs of Staff notified General Douglas MacArthur of the President's plan in a message radioed from Washington on 20 January. They informed him of the prevalent feeling in the United Nations that the UN Command should make no major advance above the Ch'ongch'on before the presidential appeal was delivered and the reactions to it determined. They also asked for his recommendations on how much freedom of ground action UN forces should have in the vicinity of the parallel during the diplomatic effort to provide for their security and to allow them to maintain contact with the PVA/KPA. That same day, Patton assembled Corps and Division commanders at his Yeoju headquarters and advised them that ceasefire negotiations and future US Government decisions might compel the Eighth Army to adopt a static defense. Because of its inherent rigidity, such a stance would require strong leadership and imaginative tactical thinking, he warned, to stand off a numerically stronger enemy that might not be similarly inhibited in the choice of tactics. The Eighth Army meanwhile would continue to move forward and in the next advance would cross the Ch'ongch'on. MacArthur, who had been pressing Washington for decisions favoring a military, not a diplomatic, solution to the war, told Patton when informed of his intentions: "Eighth Army is yours, George. Do what you think best."

On 23 January, two days before the offensive was scheduled to continue, Patton toured I and IX Corps to motivate the men for the pending operation. In the speeches, Patton urged his soldiers to do their duty regardless of personal fear, and he exhorted them to aggressiveness and constant offensive action. Patton's profanity-laced speaking resounded well with his men, but when news of the speech reached Bradley and Truman, they were furious. Both Patton and MacArthur's public statements had become increasingly irritating to Truman, as he and Bradley now contemplated relieving Patton of his command.

I don't want any more messages saying 'I'm holding my position.' We've held enough positions in this war. We'll not hold any goddamned line anymore. We'll advancing constantly and we're not interested in holding anything except the enemy's balls. Our plan of operation is to advance and keep on advancing. And we'll win this war, but we'll win it only by fighting and showing the Communists that we've got more guts than they have or ever will have. We're not just going to shoot the bastards, we're going to rip out their living goddamned guts and use them to grease the treads of our tanks. We're going to murder those lousy cocksuckers and throw them out of Korea. And then we will go all the way to goddamned Peking! [...] I have no particular desire to understand these Communist son of bitches them except to ascertain how much lead or iron it takes to kill them. They are all out son of bitches and barbarians with no regard for human life. So this war can only have one outcome. An outcome where the hammer and the sickle are no more welcomed in the world than is the goddamned swastika!

In the I Corps' zone, the 25th Infantry Division crossed the Ch'ongch'on before daylight on 25 January. The UN forces pushed through moderate resistance, much of it in the form of machine gun, mortar fire and antitank and antipersonnel mines. In the west, pushing scattered People's Volunteer Army (PVA) 65th Army forces out of position while using reconnaissance by fire and occasionally by assault, and turning back a few light counterattacks, the 1st Cavalry Division had advanced 65 km and reached Kusong by 28 January. Further east, the 5th Armoured Division and the Turkish Brigade of the IX Corps had captured Han-dong and Chungbong-don by 30 January, while the US 25th Infantry Division took the heights overlooking the Taechon Reservoir on 1 February. On the coast, the 1st Marine Division had advanced towards the Chosin Reservoir, while establishing supply points and airfields along the way at Hagaru-ri and Koto-ri. The Korean III Corps advanced eastwards towards Wonpung-ni and Pukchŏng, reaching the line by 20 February, where they subsequently formed a defensive line to protect the right flank of US X Corps. When Bradley and Truman learned of the continued advance by the Eight Army, they were furious.

At 17:00 on 2 February, 25th Division air observers reported a long column of trucks, some towing artillery pieces, moving down the Inhwa-dong–Kusong road toward the Turkish Brigade. Aircraft and artillery attacked the trucks until they dispersed off the road into wooded areas. By 18:00 PVA infantry were seen marching southwards toward Kusong in close column and just before dark were observed occupying foxholes along the sides of the road. Ten batteries of artillery kept the road and the suspected enemy artillery positions under fire. Immediately north of the city, artillery pilots spotted PVA columns nearing 24th Division lines late in the afternoon and brought them under fire as they came within range. The approaching forces simply accepted casualties as they massed above the center of the division front. At 19:00 the 24th Division commander, General Blackshear M. Bryan, notified I Corps' headquarters that he expected to be attacked in about two hours. "I think this is what we have been waiting for," he added. Bryan's prediction of attack proved correct. The initial assault of the PVA/KPA spring offensive opened at 18:00.

Chinese Fourth Phase Offensive (February – March 1951)

PVA Commander-in-Chief Peng Dehuai and the rest of his command, determined to evict the UN forces from Korea permanently, had reformed his frontline forces and amassed a strike force of three field armies and three KPA corps, totaling 700,000 men. Of these, he ordered 270,000 from the III, IX and XIX Army Groups to be directed for an assault towards Seoul, while the rest were deployed elsewhere on the battlefront with 214,000 men serving as their strategic reserve to be committed for support purposes. The PVA 3rd and 19th Armies, under orders from Chairman Mao Zedong, began to enter Korea in January 1951, alongside four field artillery divisions, two long range artillery divisions, four anti-aircraft divisions, one multiple rocket launcher division, and four tank regiments equipped with the T-34-85, marking the first time the Chinese had deployed such weapons in the war.

At 18:00 on 2 February, the PVA launched the Fourth Phase Offensive. The first thrust of the offensive fell upon I Corps, which fiercely resisted in the Battle of Kusong (2–4 February 1951) and the Battle of Taeryung River (5–8 February 1951), blunting the impetus of the offensive, which was halted at the Idaho Line along the Ch'ongch'on River. Casualty ratios were grievously disproportionate; Peng had expected a 1–1 or 2-1 ratio, but instead, Chinese combat casualties from 2 to 11 February totaled between 40,000 and 60,000 compared to only 4,000 for the UN – a casualty ratio between 10–1 and 15–1. By the time Peng had called off the attack in the western sector on 11 February, the three participating armies had lost a third of their front-line combat strength within a week. However, UN morale suffered a devastating blow when Patton, while visiting the troops of the US 25th Infantry Division, was severly injured by mortar fire on 7 February and was evacuated to Japan for medical treatment. Lieutenant General Matthew Ridgway assume tdhe command of the US Eighth Army on 13 January, and the arrival of the charismatic revived the morale of the UN forces. He immediately ordered all the defenses from the Pusan perimeter and the Walker Line to be transported to the Idaho Line, in order to form a fortified defensive line.

On 25 February 1951, the PVA commenced the second impulse of the offensive and attacked the ROK and US IX and X Corps in the east. 370,000 PVA and 64,000 KPA troops had been mobilized for the second step of the Fifth Phase Offensive, with the bulk attacking in the eastern sector with about a quarter attempting to pin the US I Corps in the western sector. After initial success, culimating with the collapse of the ROK 6th Infantry Division its withdrawal from Huichonb to Hyangsan, they were halted by 4 March and repulsed over the following days. At month's end, the Chinese planned the third step of the Fifth Phase Offensive (withdrawal), which they estimated would take 10 to 15 days to complete for their 340,000 remaining men, and set the retreat date for the night of 23 March. They were caught off guard when the US Eighth Army counterattacked and regained the Kansas Line on the morning of 12 March, 23 hours before the expected withdrawal. The surprise attack turned the retreat into "the most severe loss since our forces had entered Korea"; from 14 to 21 March, the PVA had suffered another 45,000 to 60,000 casualties before their remaining men managed to evacuate back north. Per official Chinese statistics, the Fourth Phase Offensive as a whole had cost the PVA 102,000 men (85,000 killed/wounded, 17,000 captured), with unknown but significant losses for the KPA.

The UN's Idaho Line halt and subsequent counterattacks began the stalemate that lasted until the armistice of 1952. The disastrous failure of the Fourth Phase Offensive (which Peng later recalled as one of only four mistakes he made in his military career) "led Chinese leaders to change their goal from driving the UNF out of Korea to merely defending China's security and ending the war through negotiations."

Stalemate and armistice negotiations (April 1951 – August 1952)

For the remainder of the war, the UN and the PVA/KPA fought but exchanged little territory, as the stalemate held. The bombing campaign of North Korea continued, and protracted armistice negotiations began on 14 April 1951 at Kanggye, the temporary capital of North Korea located in PVA/KPA held territory. On the Chinese side, Zhou Enlai directed peace talks, and Li Kenong and Qiao Guanghua headed the negotiation team. Combat continued while the belligerents negotiated; the goal of the UN forces was to hold the Idaho Line to avoid losing territory. The PVA and the KPA attempted similar operations and later effected military and psychological operations in order to test the UN Command's resolve to continue the war. The two sides constantly traded artillery fire along the front, the American-led forces possessing a large firepower advantage over the Chinese-led forces. For example, in the last three months of 1951 the UN fired 3,553,518 field gun shells and 2,569,941 mortar shells, while the communists fired 377,782 field gun shells and 672,194 mortar shells: an overall 5.83:1 ratio in the UN's favor. The communist insurgency, reinvigorated by North Korean support and scattered bands of KPA stragglers, also resurged in the south. In the autumn of 1951, Ridgway ordered Major General Paik Sun-yup to break the back of guerrilla activity. From December 1951 to March 1952, ROK security forces claimed to have killed 11,090 partisans and sympathizers and captured 9,916 more.

The principal battles of the stalemate include the Battle of Bloody Ridge (18 August–15 September 1951), the Battle of Hyangsan (31 August-21 September 1951), the Battle of Heartbreak Ridge (13 September–15 October 1951), and the Battle of Kujang (26 June–4 August 1952).

PVA troops suffered from deficient military equipment, serious logistical problems, overextended communication and supply lines, and the constant threat of UN bombers. All of these factors generally led to a rate of Chinese casualties that was far greater than the casualties suffered by UN troops. The situation became so serious that, in November 1951, Zhou Enlai called a conference in Shenyang to discuss the PVA's logistical problems. At the meeting it was decided to accelerate the construction of railways and airfields in the area, to increase the number of trucks available to the army, and to improve air defense by any means possible. These commitments did little to directly address the problems confronting PVA troops.

In the months after the Shenyang conference, Peng Dehuai went to Beijing several times to brief Mao and Zhou about the heavy casualties suffered by Chinese troops and the increasing difficulty of keeping the front lines supplied with basic necessities. Peng was convinced that the war would be protracted and that neither side would be able to achieve victory in the near future. On 24 February 1952, the Military Commission, presided over by Zhou, discussed the PVA's logistical problems with members of various government agencies involved in the war effort. After the government representatives emphasized their inability to meet the demands of the war, Peng, in an angry outburst, shouted: "You have this and that problem... You should go to the front and see with your own eyes what food and clothing the soldiers have! Not to speak of the casualties! For what are they giving their lives? We have no aircraft. We have only a few guns. Transports are not protected. More and more soldiers are dying of starvation. Can't you overcome some of your difficulties?" The atmosphere became so tense that Zhou was forced to adjourn the conference. Zhou subsequently called a series of meetings, where it was agreed that the PVA would be divided into three groups, to be dispatched to Korea in shifts; to accelerate the training of Chinese pilots; to provide more anti-aircraft guns to the front lines; to purchase more military equipment and ammunition from the Soviet Union; to provide the army with more food and clothing; and, to transfer the responsibility of logistics to the central government.

With peace negotiations ongoing, the Chinese attempted one final offensive in the final weeks of the year to capture territory: on 10 April 1952, 30,000 Chinese troops struck two South Korean and one US divisions on a 13 km (8 mi) front near Kaech'ŏn, and on 13 July, 80,000 Chinese soldiers struck the east-central Hamhung sector, with the brunt of their attack falling on four South Korean divisions. In both cases, the Chinese had some success in penetrating South Korean lines, but failed to capitalize, particularly when the US forces present responded with overwhelming firepower. Chinese casualties in their final major offensive of the war (above normal wastage for the front) were about 72,000, including 25,000 killed in action compared to 14,000 for the UN (the vast majority of these deaths were South Koreans, though 1,611 were Americans).

The on-again, off-again armistice negotiations continued for a year. A major, problematic negotiation point was prisoner of war (POW) repatriation. The PVA, KPA and UN Command could not agree on a system of repatriation because many PVA soldiers refused to be repatriated back to the north, which was unacceptable to the Chinese. A Neutral Nations Repatriation Commission, under the chairman Indian General K. S. Thimayya, was subsequently set up to handle the matter. Meanwhile, Indian Prime Minister Jawaharlal Nehru's government suggested to the UN allies that China might accept a ceasefire in Korea and Korean unification if the US allowed Communist China to take control of China's seat in the UN Security Council still controlled by the Nationalist Chinese government now exiled on the island of Taiwan.

With the United Nations' acceptance of India's proposed Korean War armistice, the KPA, the PVA and the UN Command signed the Korean Armistice Agreement on 4 August 1952. North Korean president Kim Il-Sung initially refused to sign the agreement, until pressured by Stalin.


After the war, Operation Glory was conducted from July to November 1953, to allow combatant countries to exchange their dead. The remains of 4,167 US Army and US Marine Corps dead were exchanged for 13,528 PVA dead, and 546 civilians dead in UN prisoner-of-war camps were delivered to the South Korean government. After Operation Glory, 416 Korean War unknown soldiers were buried in the National Memorial Cemetery of the Pacific (The Punchbowl), on the island of Oahu, Hawaii. Defense Prisoner of War/Missing Personnel Office (DPMO) records indicate that the PRC transmitted 1,394 names, of which 858 were correct. From 4,167 containers of returned remains, forensic examination identified 4,219 individuals. Of these, 2,944 were identified as from the US, and all but 416 were identified by name.

Peace negotiations and the Prague Peace Accords (August 1951 – May 1952)

Under the Armistice Agreement, the belligerents established the Korean Demilitarized Zone (DMZ), along the frontline which vaguely follows the Ch'ongch'on River. The DMZ runs along the Ch'ongch'on to the Chosin Reservoir and southeast to Hamhung. The armistice also called upon the governments of South Korea, North Korea, China and the United States to participate in continued peace talks. However, the primary negotiations that led to the agreement were carried out during secret negotiations between US Secretary of State Dean Acheson and Chinese Foreign Minister Zhou Enlai, which began on 6 April 1951. With the mediation of India and Czechoslovakia, the Truman Administration agreed to give the Chinese seat at the UN Security Council to the People's Republic of China instead of Taiwan. In return, China would allow for the reunification of Korea and the deployment of US forces in Korea, provided the Demilitarized Zone remained in place.

Consequently, the U.S. brought great diplomatic pressure upon their Korean allies to sign the peace treaty. Truman pledged to provide continued substantial aid to both Korea and Taiwan. The Soviet Union and China brought pressure on Kim Il-sung to sign the treaty. Kim was summoned to Moscow for six weeks in the autum of 1951, where he refused Stalin's demands. Subsequently, Kim was forced into exile in the Soviet Union after being removed from power by Pak Chang-ok and Choe Chang-ik after Soviet and Chinese pressure on 12 March 1952.

The peace agreement was signed by the leaders of the official delegations on 15 May 1952 in Prague, Czechoslovakia. The delegations were led by US Secretary of State Acheson, Chinese Foreign Minister Zhou, South Korean Foreign Minister Byeon Yeong-tae and North Korean Foreign Minister Pak Hon-yong. The agreement called for:

  • Korean Demilitarized Zone (DMZ) to be monitored by the United Nations Supervisory Commission (UNSC), composed of Canada, Czechoslovakia, Poland, Hungary, Romania and Sweden. The UNSC would implement the ceasefire.
  • The withdrawal of all Chinese forces.
  • The UN forces would remain as a police force.
  • The return of prisoners of war.
  • Organize free elections throughout all of Korea, under UN supervision.
  • The establishment of a "National Council of National Reconciliation and Concord" composed of a government, communist and neutralist side to implement democratic liberties in Korea.

Casualties

Aftermath

Korea

The Korean Peace Accord provided for the establishment of the Korean Demilitarized Zone (DMZ) which was 1,370 kilometres long, and about 6 kilometres wide. Since 1952, the DMZ has been monitored by the United Nations Supervisory Commission (UNSC) and stationed stationed near the DMZ. There have been various incidents in and around the DMZ, with military and civilian casualties on both sides.

As stipulated in the peace accord, parliamentary and presidential elections took place throughout Korea on 20 May 1954, with supervision from the United Nations. The parliamentary election resulted in a victory for the Liberal Party, which won 114 of the 203 seats, while the People's Party of Korea received 68. In the presidential election, Syngman Rhee won 64.6% of the vote. While the election result were praised by the US, the Soviets and Chinese criticized Rhee for amending the constitution so that the president would be elected by popular vote, instead of the legislature. President Rhee had the amendment pass in July 1952, after using police and military to threaten lawmakers. Following the election, Rhee consolidated his powers and modified the constitution to remove the two-term restriction. Despite protests from the opposition Rhee enacted laws that severely curtailed political dissent, and his government continued to suppress dissidents and the opposition. Rhee was eventually forced to resign on 26 April 1960 following the student-led April Revolution.

Postwar recovery in Korea stagnated in the first postwar decade. In 1953, Korea and the United States signed a Mutual Defense Treaty. In 1960, the April Revolution occurred and students joined an anti-Syngman Rhee demonstration; 142 were killed by police; in consequence Syngman Rhee resigned and left for exile in the United States. Park Chung-hee's May 16 coup enabled social stability. From 1965 to 1973, Korea dispatched troops to South Vietnam and received $235,560,000 in allowance and military procurement from the United States. GNP increased fivefold during the Vietnam War. South Korea industrialized and modernized. Korea had one of the world's fastest-growing economies from the early 1960s to the late 1990s. In 1957 Korea had a lower per capita GDP than Ghana, and by 2010 it was a developed country and ranked thirteenth in the world (Ghana was 86th).

United States

While Truman received praise from his European allies and Canada for reuniting Korea and recognizing the People's Republic of China, the peace agreement was met with condemnation from the Republicans, and in particular by members of the China Lobby. Some of the lobby's most hard-line anti-communists — Republican Representative Walter H. Judd and Republican senators William F. Knowland, Robert Taft, and Joseph R. McCarthy — denounced the peace treaty an act of treason which would sacrifice Chiang Kai-shek and the Kuomintang to the communists, and called for immediate impeachment proceedings against Truman. On the Senate floor, Taft said:

Truman must be impeached and convicted. Giving in to the Communists is the culmination of series of acts which have shown that he is unfit, morally and mentally, for his high office. The American nation has never been in greater danger. It is led by a fool who is surrounded by knaves.

Truman entered 1952 with his popularity plummeting, according to polls, as Senator Joseph McCarthy's anti-Communist crusade was stirring public fears of an encroaching "Red Menace", and the disclosure of widespread corruption among federal employees (including some high-level members of Truman's administration) left Truman at a low political ebb.

Since the end of the Korean War, the US has had a major military presence in Korea. The United States Forces Korea (USFK), comprising the Eighth U.S. Army (EUSA), U.S. Air Forces Korea (Seventh Air Force), U.S. Naval Forces in Korea (CNFK), U.S. Marine Forces Korea (MARFORK) and Special Operations Command Korea (SOCKOR), the USFK currently has a strength of 23,500 men, and conducts routine exercises with the Korean Armed Forces.

Korean anti-Americanism after the war was fueled by the presence and behavior of US military personnel (USFK) and US support for Park's authoritarian regime, a fact still evident during the country's democratic transition in the 1980s. However, anti-Americanism has declined significantly in Korea in recent years, from 46% favorable in 2003 to 74% favorable in 2011, making South Korea one of the most pro-US countries in the world.

A large number of mixed-race "GI babies" (offspring of US and other UN soldiers and Korean women) were filling up the country's orphanages. Because Korean traditional society places significant weight on paternal family ties, bloodlines, and purity of race, children of mixed race or those without fathers are not easily accepted in South Korean society. International adoption of Korean children began in 1953. The US Immigration Act of 1952 legalized the naturalization of non-blacks and non-whites as US citizens and made possible the entry of military spouses and children from South Korea after the Korean War. With the passage of the Immigration Act of 1965, which substantially changed US immigration policy toward non-Europeans, Koreans became one of the fastest-growing Asian groups in the United States.

Racial integration efforts in the U.S. military began during the Korean War, where African Americans fought in integrated units for the first time. President Truman signed Executive Order 9981 on July 26, 1948, calling on the armed forces to provide equal treatment and opportunity for black servicemen. The extent to which Truman's 1948 orders were carried out varied among the various branches of the military, with segregated units still in deployment at the start of the war, and eventually being integrated towards the end of the war. The last large segregated operational unit was the U.S. 24th Infantry Regiment which was deactivated on October 1, 1951.

Soviet Union

The war was a political disaster for the Soviet Union. Its central objective, the unification of the Korean peninsula under the Kim Il-Sung regime, was not achieved. Relations with communist ally China were seriously and permanently spoiled, leading to the Sino-Soviet split that lasted until the rapproachment launched by President Vladimir Putin in 2000.

The United States' strong resistance to the invasion may have prevented a Soviet intervention in Yugoslavia during the Tito-Stalin split. The war, meanwhile, united the countries within the capitalist bloc: the Korean War accelerated the conclusion of a peace agreement between the U.S. and Japan, the warming of West Germany's relations with other western countries, creation of military and political blocs ANZUS (1951) and SEATO (1954). However, because of the war, the authority of the Soviet State grew, which showed in its readiness to interfere in developing countries of the Third World, many of which after the Korean war went down the socialist path of development, after selecting the Soviet Union as their patron.

It is generally assumed that the war was a heavy burden on the national economy of the Soviet Union, which was still suffering from the effects of World War II. Expenditures for defense certainly grew more sharply than they otherwise would have. However, it has been claimed that in fact much of the payment for the Soviet contribution to the war effort was made by China (which perhaps goes some way towards explaining the eventual split between the two countries).

People's Republic of China (PRC)

The peace agreement with the United States benefited the PRC immensely and greatly increased its security for the rest of the Cold War. The PRC was admitted to the UN and took over the Chinese seat at the UN Security Council from the ROC. It has been argued that the United States, on the other hand, saw fewer benefits than it had hoped for, inasmuch as China continued to back America's enemies.

On 14 October 1952, a draft resolution was submitted by the Soviet Union and seven other states to "restore to the People's Republic of China all its rights and expel forthwith the representatives of Chiang Kai-shek." The voting took place on 18 November 1952. In the first vote held, the Assembly approved the US-backed motion to allow the PRC to join the UN as "China's representative", while allowing the ROC to remain a regular UN member. The motion was approved by a vote of 41 to 12, with 6 abstentions. The Assembly then adopted the draft a roll-call vote of 31 to 22, with 6 abstentions, as Resolution 546. The Beijing government began representing China at the UN from 15 December 1952 and its delegates were seated at the UN Security Council meeting held on 16 December 1952, the first such meeting where representatives of the Beijing government represented China.

The PRC had sent some of its best units to join the war. Although the People's Liberation Army (PLA) had some initial success, losses (both on the battlefield as well as in material and casualties) exposed the PLA's weaknesses in firepower, air support, logistics, and communication. As a result, the PLA was given a new mandate to modernize and professionalize itself. This ran counter to the PLA's previous mandate that put dogma before expertise and modernization. The commander of the PLA's forces in Korea during the war, marshal Peng Dehuai, was made the government's first minister of defense to implement the changes and reforms such as modernization of weaponry, training and discipline, the rank system, and conscription.

Mao Zedong's decision to take on the United States in the Korean War was a direct attempt to confront what the Communist bloc viewed as the strongest anti-Communist power in the world, undertaken at a time when the Chinese Communist regime was still consolidating its own power after winning the Chinese Civil War. Mao supported intervention not to save North Korea, but because he believed that a military conflict with the US was inevitable after the US entered the war, and to appease the Soviet Union to secure military dispensation and achieve Mao's goal of making China a major world military power. Mao was equally ambitious in improving his own prestige inside the communist international community by demonstrating that his Marxist concerns were international. Protecting the Manchurian industrial zone was also one of the major reasons China entered the war. In his later years, Mao believed that Stalin only gained a positive opinion of him after China's entrance into the Korean War. Inside mainland China, the war was disaster, but nonetheless improved the long-term prestige of Mao, Zhou, and Peng because of their diplomatic recognition by the United States and their admittance to the United Nations. This allowed the Chinese Communist Party to increase its legitimacy while weakening anti-Communist dissent.

The Chinese government has encouraged the point of view that the war was initiated by the United States and South Korea, though ComIntern documents have shown that Mao sought approval from Joseph Stalin to enter the war. In Chinese narrative, the Chinese war effort is considered as an example of China's engaging the strongest power in the world with an under-equipped army, forcing it to retreat, and fighting it to a military stalemate before they agreed to give them international recognition by giving them the seat at the UN Security Council. These successes were contrasted with China's historical humiliations by Japan and by Western powers over the previous hundred years, highlighting the abilities of the PLA and the Chinese Communist Party. However, the most significant negative long-term consequence of the war for China was that it led the United States to guarantee the safety of Chiang Kai-shek's regime in Taiwan, effectively ensuring that Taiwan would remain outside of PRC control through the present day. Mao had also discovered the usefulness of large-scale mass movements in the war while implementing them among most of his ruling measures over PRC. Finally, anti-U.S. sentiments, which were already a significant factor during the Chinese Civil War, was ingrained into Chinese culture during the Communist propaganda campaigns of the Korean War.

While China's admittance to the UN and recognition by the United States was considered a victory for Mao, China also lost the opportunity to reunify Taiwan. Initially, the United States had abandoned the KMT and expected that Taiwan would fall to Beijing anyway, so the basic U.S. policy was to "wait and see" on the assumption that Taiwan's fall to Communist China was inevitable. However, the North Korean invasion of South Korea, in the context of the Cold War, meant U.S. President Truman intervened again and dispatched the Seventh Fleet to "neutralize" the Formosa (Taiwan) Strait.

Republic of China (Taiwan)

After the US signed the peace accord with China, the Taiwan issue remained a major source of contention. After the UN General Assembly Resolution 546 admitted the People's Republic of China (PRC) into the UN and gave them the Chinese seat in the UN Security Council at the expense of the the Republic of China, the ROC immediately condemned the United States and the UN, claiming they had betrayed the "ideals upon which the UN was founded". The Peace accord and the passing of the UN GAR 546 lead to rampant protests in both Taiwan and in the US. The Republic of China would remain a regular UN member for the next two decades until the admission of newly independent developing nations in the 1960s gradually turned the General Assembly from being Western-dominated to being dominated by countries sympathetic to the PRC. On 25 October 1971, the UN General Assembly adopted Resolution 2758, with 76 countries supporting, 35 countries opposing, 17 countries abstaining, and 3 countries non-voting, withdrawing recognition of the representatives of Chiang Kai-shek and recognizing the Government of PRC as the only legitimate representative of China to the United Nations. At a Security Council meeting on 23 November 1971, after the General Assembly passed Resolution 2758, removing the ROC their representation in the UN.

The War in Korea nevertheless played an important role in sustaining the Republic of China's economic stability. Until the war in Korea, the US had largely abandoned the Nationalist government of Generalissimo Chiang Kai-shek, whose forces had retreated to Taiwan after their defeat at the hands of Mao Zedong's Communists in the Chinese Civil War. Indeed, the US had little involvement in that conflict, beyond supplying surplus material to the Nationalists. However, the PRC's involvement in the Korean War rendered any U.S. policy that would have allowed Taiwan to fall under PRC control untenable. This saw the abandonment of the American policy to let Taiwan join the communist Chinese state, the policy which existed prior to the war. Truman's decision to send the US Seventh Fleet to the Formosa Strait as well as an increase in aid in order to deter the PRC from making any attempt to invade Taiwan, after doing nothing to prevent the Nationalists' mainland defeat in the first place, is evidence of this. In April 1953, the US Congress signed into law the Taiwan Relations Act, permitting unofficial relations with Taiwan to flourish, on the one hand, yet the right of the US to provide Taiwan with arms of a defensive character, on the other.

Also, with the peace accord the People's Republic of China pledged to abstain from a military solution to the Chinese question. The result has been that, today, any effort by the PRC to invade the island, or otherwise coerce the people there into an arrangement of political unity with the Communist controlled mainland, would be difficult at best to accomplish, and may be impossible without a great deal of bloodshed. While economic ties between the PRC and ROC have grown immensely since the 1990s, thus achieving a degree of interdependency that would have been unimaginable even twenty years ago; political diplomacy between the ROC and mainland China remains strained, and successive governments in Taiwan have consistently, if sometimes obliquely, signaled their determination to remain independent for the foreseeable future.

See also

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