Soviet–Japanese War (WFAC)

Soviet–Japanese War
Part of World War II
Japanese soldiers watching the shelling of Vladivostok on 12 September 1939.
Date 19 April 1939 – 12 August 1940 (1 year, 3 months, 3 weeks and 3 days) Place Manchuria and the Mongolian-Manchukuoan border Result Pyrrhic Japanese victory Tactical Soviet and Mongolian victory at the Mongolian-Manchukuoan border Japan captures Vladivostok Soviet–Japanese Neutrality Pact The Northern Expansion Doctrine (Hokushin-ron) gets discredited
Belligerents
Empire of Japan Manchukuo	Soviet Union Mongolia
Commanders and leaders
Hirohito Kenkichi Ueda Kotaro Nakamura Pu Yi	Joseph Stalin Grigoriy Shtern Vsevolod Yakovlev Georgy Zhukov Ivan Yumashev Khorloogiin Choibalsan
Units involved
Kwantung Army Korea Army Manchukuo Imperial Army	Far Eastern Front Transbaikal Front Pacific Fleet Mongolian People's Army
Strength
Japan: 813,000 men 4,820 artillery pieces 1,110 tanks 1,100 aircraft Manchukuo: 170,000 men	Soviet Union: 650,600 men 7,800 artillery pieces 1,147 tanks 1,600 aircraft Mongolia: 16,000 men
Casualties and losses
Japan: 210,000 killed 250,700 wounded or sick (including at least 63,100 sick or frostbitten) 6,000 captured 520 tanks lost 378 aircraft lost	Soviet Union: 176,320 killed 188,520 wounded 210,000 captured 620 tanks lost 420 aircraft lost Mongolia: 2,000 casualties

The Soviet–Japanese War (19 April 1939 – 12 August 1940) was a conflict fought among the Soviet Union, Mongolia, Japan and Manchukuo during 1939 and 1940 as part of World War II. The major theatres of operations were Vladivostok and the Primorsky Krai of the Soviet Far East, the border region between Mongolia and Manchuria, and the seas around Korea, Japan and the Yellow Sea.

Historical background

The roots of anti-Soviet sentiment in Imperialist Japan began before the foundation of the Soviet Union. For most of the first half of the twentieth century there was considerable tension between Moscow, Tokyo and Beijing along their common borders in what is now North East China. The Chinese Eastern Railway or (CER) was a railway in northeastern China (Manchuria). It connected China and the Russian Far East. The southern branch of the CER, known in the West as the South Manchuria Railway, became the locus and partial casus belli for the Russo-Japanese War (1904–05). Eager to further limit Russian influence in East Asia after the Russo-Japanese War and contain the spread of Bolshevism, the Japanese sent some 70,000 troops into Siberia from 1918 to 1922 as part of the Siberian Intervention on the side of the White Movement, occupying Vladivostok and many key points in Far Eastern Russia east of Lake Baikal.

Following the international withdrawal from Russian territory, the Imperial Japanese Army, mindful of the potential of the USSR as a military power and keeping with the convention of Russia as a traditional enemy, made contingency plans for war with the Soviet Union. At first they were defensive, assuming an attack from the Red Army into Chinese territory which would be parried by a Japanese counter-thrust from Korea; the decisive battlefield would be in southern Manchuria. Following the Japanese invasion of Manchuria and its annexation in 1931, Japanese and Soviet troops for the first time faced one another along a border thousands of kilometers long. To protect the Japanese Manchukuo puppet state and to gain the initiative, the IJA adopted a policy of halting any Soviet advance along the border and fighting the greater part of the war in Siberia – an "epoch making change" in Japanese strategic thought which led to offensive planning that would not be reversed until 1945. Over time, Japanese operational plans evolved from small operations into multi-stage offensive actions aimed first against Vladivostok and eventually the entirety of the Soviet Far East as far as Lake Baikal.

Following the Japanese invasion of Manchuria in 1931, violations of the vaguely defined Manchukuo-Mongolia-USSR border were frequent. Most of these were misunderstandings, but some were intentional acts of espionage. According to the IJA, between 1932 and 1934, 152 border disputes occurred, largely because the Soviets found it necessary to gather intelligence inside Manchuria. For their part, the Soviets blamed the Japanese for 15 cases of border violation, 6 air intrusions, and 20 episodes of "spy smuggling" in 1933 alone. Hundreds more violations were reported by both sides throughout the following years. To make matters worse, Soviet-Japanese diplomacy and trust had declined even further in these years, with the Japanese being openly called "fascist enemies" at the Seventh Comintern Congress in July 1935.

Before the outbreak of Second Sino-Japanese War in July 1937, Soviet-Japanese relations began to deteriorate rapidly. The Kwantung Army responsible for governing Manchuria, previously elevated from a minor garrison command to the level of a general headquarters, became increasingly bellicose towards its northerly neighbor. The army began to act as a "self-contained, autonomous" entity independent from the central government in Tokyo. With this conduct came a corresponding rise in Soviet-Japanese border conflicts, culminating in the Kanchatzu Island Incident in which a Soviet river gunboat was sunk by Japanese shore batteries, killing 37 personnel. This, other episodes, and the reciprocal political and military subversion by both sides (the Japanese recruiting White Russian agents and the Soviets sending material support to China, before and during the war with Japan) led figures on both sides to conclude that a future war was likely, even, where some in the Kwantung Army were concerned, inevitable.

After war began between China and Japan in July 1937, Japanese options for Manchuria became very limited. The Soviets capitalized on this vulnerability by signing a non-aggression pact with China and supplying them with arms and equipment. The Japanese predicament did not prevent them from continuing to formulate war plans against the USSR; their operational plan of 1937, though crude and deficient from a logistical perspective, provided the basis for all subsequent developments through 1944. The plan (and most others after it) called for a sudden initial onslaught against the Soviet 'Maritime Province' facing the Pacific Ocean (also referred to as "Primorye"), coupled with holding actions in the north and west. Should the first phase meet with success, the other fronts would likewise transition to the offensive after the arrival of reinforcements.

In 1936, Soviet leader Joseph Stalin began the Great Purge of opposition including the Red Army officer corps, killing or incarcerating tens of thousands of high-ranking figures, often on trumped up or fictitious charges. The Red Army's fighting power was severely weakened, an observation seemingly confirmed by its relatively poor showings at the Battle of Lake Khasan in 1938 and the invasion of Poland later that year. Fear led people to defect or flee abroad; on 13 June 1938, Genrikh Lyushkov, Chief of the Far Eastern Department of the NKVD (Soviet secret police), crossed the border into Manchuria and turned himself in to the IJA, bringing with him a wealth of secret documents on Soviet military strengths and dispositions in the region. Lyushkov's treason was a major intelligence coup for Japan.

The border violations culminated in the Battle of Lake Khasan (29 July – 11 August 1938), also known as the Changkufeng Incident, in which a Japanese military incursion from Manchukuo into territory claimed by the Soviet Union. This incursion was founded in the belief of the Japanese side that the Soviet Union misinterpreted the demarcation of the boundary based on the Convention of Peking treaty between Imperial Russia and the former Qing-Dynasty China (and subsequent supplementary agreements on demarcation), and furthermore, that the demarcation markers had been tampered with. The incursion was triggered in part by the Soviet Far East Army and the NKVD reinforcing its Khasan border with Manchuria, and in part by Lyushkov's defection one month before, as he had provided the Japanese with intelligence on the poor state of Soviet Far Eastern forces and the purge of army officers. The Japanese 19th division expelled a Soviet garrison from the disputed area, and repulsed numerous counterattacks by an overwhelmingly more numerous and heavily armed Soviet force. Both sides took heavy losses, though Soviet casualties were nearly three times higher than Japanese casualties, and they lost dozens of tanks. The conflict was resolved diplomatically on 10 August, when the Japanese ambassador in Moscow asked for peace. The Japanese troops withdrew the next day, and the Soviets again occupied the now-empty area.

Prelude

Map of the political situation in Eastern Asia in the spring of 1939.

  Soviet Union

  Mongolia (puppet state of the USSR)

  Japan and occupied territory

  Puppet states of Japan

  China

Opposing forces and plans

Japan

In 1936, Soviet leader Joseph Stalin began the Great Purge of opposition including the Red Army officer corps, killing or incarcerating tens of thousands of high-ranking figures, often on trumped up or fictitious charges. The Red Army's fighting power was severely weakened, an observation seemingly confirmed by its relatively poor showings at the Battle of Lake Khasan in 1938 and the war against Poland in 1938.

Independent of their yearly planning, in 1938–39 the Operations Bureau of the Japanese Army General Staff and the Kwantung Army cooperated on an operational plan under the umbrella term "Operational Plan no. 8," or the "Hachi-Go" plan. These two schemes, designated Concepts "A" and "B," examined the possibility of an all-out war with the Soviet Union beginning in 1943. Both were far larger than anything previously conceived of by the Japanese, envisioning a commitment of 50 IJA divisions against an expected 60 for the Soviets to be delivered incrementally from China and the Home Islands. Concept A followed a more traditional setup by considering simultaneous Japanese offensives in the East and North while holding in the West, involving a 20-15-15 divisional apportionment among the eastern, northern and western fronts in three months, against an anticipated Soviet 20-15-25 divisional deployment in the same time. Concept B boldly called for an initial Kwantung Army offensive on the western front into the vast steppe between the Great Khingan Mountains and Lake Baikal in the hopes of scoring a knockout blow early – thus dooming the defenders of Primorye and Vladivostok to defeat in detail. The Japanese deployment would be 10-10-25 against Soviet forces estiamted at 18-12-30.

The scope of operations was enormous: the two forces would have fought over a frontage nearly 5,000 kilometers (3,100 miles) in length, with Japan's final objectives being up to 1,200 km (750 mi) deep into Soviet territory. Beset by apprehensions concerning the feasibility of breaking through the powerful Soviet defences on the eastern front, the military authorities in both Tokyo and Hsinking preferred the second alternative, but it was soon realized that an immense railroad construction program would be indispensable, as would the amassing of great numbers of motor vehicles and the stockpiling of huge stores of matériel on the Hailar Plain. Specifically with regard to Concept B, the railway network in Manchuria had not been sufficiently expanded to facilitate such a far-reaching offensive and supply stocks on hand in the country were seriously below the required levels. Furthermore, the ongoing war in China precluded the concentration of the planned 50 divisions without fatally weakening the Japanese effort there. Additionally, Imperial General Headquarters concluded that in order to sustain a drive out to Lake Baikal, a fleet of some 200,000 trucks would be necessary, a number more than twice as great as anything the entire Japanese military possessed at any given time.

Order of Battle

Japan

Kwantung Army

General Kenkichi Ueda.

CO: General Kenkichi Ueda

Chief of Staff: Lieutenant General Rensuke Isogai

Headquarters: Hsinking, Manchukuo

3rd Army

CO: General Hayao Tada

9th IJA Division (Lt.Gen. Ryosuke Yoshizumi)

11th IJA Division (Lt.Gen. Shoichi Naito)

12th IJA Division (Lt.Gen. Kiyotaro Uemura)

19th IJA Division (Lt.Gen. Hada Jūichi)

21st IJA Division (Lt.Gen. Washizu Shōhei)

37th IJA Division (Lt.Gen. Kenkichi Hirata)

38th IJA Division (Lt.Gen. Yoji Fujii)

108th IJA Division (Lt.Gen. Koyama Shimomoto)

114th IJA Division (Lt.Gen. Tokushige Numata)

7th IJA Artillery Brigade

2nd IJA Tank Group (Mj.Gen. Kōji Sakai)

1st Tank Regiment (31x Type 97 Chi-Ha medium tanks, 17x Type 95 Ha-Go light tanks, 3x Type 94 tankettes)

7th Tank Regiment (25x Type 97 Chi-Ha medium tanks, 12x Type 95 Ha-Go light tanks)

8th Tank Regiment (26x Type 89 I-Go medium tanks, 17x Type 95 Ha-Go light tanks, 4x Type 94 tankettes)

4th Army

CO: Lieutenant General Kesago Nakajima

6th IJA Division

8th IJA Division

35th IJA Division

101st IJA Division

5th IJA Artillery Brigade

3rd IJA Cavalry Brigade

5th Army

CO: General Kenji Doihara

24th IJA Division

25th IJA Division

34th IJA Division

8th IJA Artillery Brigade

6th Army

CO: Lieutenant General Rippei Ogisu

1st IJA Division

2nd IJA Division

7th IJA Division

10th IJA Division

23rd IJA Division

26th IJA Division

36th IJA Division

5th IJA Artillery Brigade

3rd IJA Cavalry Brigade

1st IJA Tank Corps (Lt.Gen. Yasuoka Masaomi)

3rd Tank Regiment (26x Type 89 I-Go medium tanks, 4x Type 97 Chi-Ha medium tanks, 7x Type 94 and 4x Type 97 Te-Ke tankettes)

4th Tank Regiment (35x Type 95 Ha-Go light tanks, 8x Type 89 I-Go medium tanks, 3x Type 94 tankettes)

10th Tank Regiment (26x Type 89 I-Go medium tanks, 17x Type 95 Ha-Go light tanks)

Kwantung Air Corps

CO: Lieutenant General Saburo Ando

Base: Hsinking

1st Air Brigade (Major General Ehashi Eijiro) - Chia-mu-ssu

1st Air Combat Group (45x Ki-27 fighter aircraft)

2nd Air Combat Group (30x Type 92, Ki-15 reconnaissance aircraft)

3rd Air Combat Group (30x Ki-32 light bombers)

7th Air Combat Group (30x Ki-1, Ki-21 heavy bombers)

13th Air Combat Group (30x Ki-32 light bombers)

55th Air Combat Group (45x Ki-27 fighter aircraft)

2nd Air Brigade (Major General Satoshi Kinoshita) - Hoeryong

6th Air Combat Group (30x Ki-32 light bombers)

9th Air Combat Group (45x Ki-10-II fighter aircraft)

46th Air Combat Group (30x Ki-15 reconnaissance aircraft)

3rd Air Brigade (Major General Tadashi Haga) - Tun-hua

8th Air Combat Group (30x Ki-15 reconnaissance aircraft and Ki-32 light bombers)

14th Air Combat Group (30x Ki-21 heavy bombers)

43rd Air Combat Group (30x Ki-32 light bombers)

Reserve

4th Air Combat Group (45x Ki-4 reconnaissance aircraft, Ki-10 and Ki-27 fighter aircraft)

5th Air Combat Group (45x Ki-27 fighter aircraft)

2nd Air Corps

CO: Lieutenant General Tetsuji Gitaga

Base: Harbin

9th Air Brigade

16th Air Combat Group (30x Ki-32 light bombers)

59th Air Combat Group (45x Ki-27 fighter aircraft)

64th Air Combat Group (45x Ki-10 and Ki-27 fighter aircraft)

12th Air Brigade

48th Air Combat Group (30x Ki-32 light bombers)

52nd Air Combat Group (45x Ki-27 fighter aircraft)

61st Air Combat Group (30x Ki-21 heavy bombers)

17th Air Brigade (Major General Ryosuke Nakanishi)

10th Air Combat Group (30x Ki-15 reconnaissance aircraft and Ki-32 light bombers)

11th Air Combat Group (45x Type 91, Type 92, Ki-27 fighter aircraft)

12th Air Combat Group (30x Ki-1, Ki-21 heavy bombers)

Korean Army

CO: General Kotaro Nakamura

Chief of Staff: Lieutenant General Kenzo Kitano

Headquarters: Keijō, Korea

20th IJA Division (Lieutenant General Ushijima Jitsutsune)

Strength: 25,000 men

Imperial Japanese Navy

Vice Admiral Soemu Toyoda.

2nd Fleet

CO: Vice Admiral Soemu Toyoda

4th Division

Takao (Takao-class heavy cruiser)

Atago (Takao-class heavy cruiser)

Chōkai (Takao-class heavy cruiser)

Maya (Takao-class heavy cruiser)

7th Division

Kumano (Mogami-class heavy cruiser)

Mikuma (Mogami-class heavy cruiser)

Mogami (Mogami-class heavy cruiser)

Suzuya (Mogami-class heavy cruiser)

2nd Destroyer Squadron

Jintsū (Sendai-class light cruiser)

2nd Destroyer Division

Harusame (Shiratsuyu-class destroyer)

Murasame (Shiratsuyu-class destroyer)

Samidare (Shiratsuyu-class destroyer)

Yudachi (Shiratsuyu-class destroyer)

8th Destroyer Division

Arashio (Arashio-class destroyer)

Asashio (Arashio-class destroyer)

Michishio (Arashio-class destroyer)

Ōshio (Arashio-class destroyer)

24th Destroyer Division

Kawakaze (Shiratsuyu-class destroyer)

Suzukaze (Shiratsuyu-class destroyer)

Umikaze (Shiratsuyu-class destroyer)

Yamakaze (Shiratsuyu-class destroyer)

6th Submarine Squadron

10 submarines

Other units:

8 minesweepers

16 patrol ships

1st KURE SNLF (Special Naval Landing Forces)

2nd KURE SNLF (Special Naval Landing Forces)

Soviet Union

Far Eastern Front

Komandarm Grigori Shtern

File:Markian Popov as Lieutenant General.jpg

Komkor Markian Popov.

CO: Komandarm Grigori Shtern

Headquarters: Vladivostok

1st Special Red Banner Army

CO: Komkor Markian Popov

Headquarters: Voroshilov

26th Rifle Corps (Pokrovka) – Komdiv Mikhail Dubkov

21st Rifle Division (Spassk-Dalny) – Kombrig Andrey Konovalov

22nd Rifle Division – Col. Vasily Semyonov

26th Rifle Division – Col. Sorokin

39th Rifle Corps – Col. Ivan Chistyakov

32nd Rifle Division (Razdol'noye) – Kombrig Alexander Batyunya

39th Rifle Division – Col. Anatoly Morozov

40th Rifle Division – Kombrig Stepan Mamonov

32nd Seperate Tank Battalion

43rd Rifle Corps – Kombrig Alexander Ksenofontov

59th Red Banner Rifle Division (Pogranichny) – Kombrig Vasily Glazunov

8th Cavalry Division (Kamen-Rybolov) – Kombrig Ivan Managarov

20th Tank Corps (Voroshilov) – Col. Sergei Denisov

8th Tank Brigade (Voroshilov) – Maj. Mikhail Pavelkin
      Strength: 216 BT-7, 48 BT-5, 47 T-26, 37 T-37A, 19 armoured cars

42nd Tank Brigade (Voroshilov) – Col. Alexey Panfilov
      Strength: 215 T-26, 74 BT-5/7, 51 T-37A, 60 armoured cars

5th Motor Rifle Brigade – Col. Konstantin Erastov

Army Reserve:

92nd Rifle Division (Barabash) – Kombrig Filipp Zhmachenko

Komandarm Ivan Konev.

2nd Special Red Banner Army

CO: Komkor Ivan Konev

Headquarters: Khabarovsk

18th Rifle Corps (Kuybyshevka-Vostochnaya) –

12th Rifle Division (Blagoveshchensk) – Kombrig Mikhail Popov

34th Rifle Division (Khabarovsk – Kombrig Afanasy Ryzhkov

Blagoveshchensk Fortified Region (Blagoveshchensk) – Kombrig Nikolai Kichaev

De-Kastri Fortified Region (De-Kastri)

Lower Amur Fortified Region (Nikolayevsk-on-Amur)

Ust-Sungari Fortified Region (De-Kastri)

Special Corps

101st Mountain Division (Petropavlovsk-Kamchatsky) – Kombrig Aksenty Gorodnyansky

105th Rifle Division (Sakhalin) – Col. Gaik Martirosian

Army Reserve

35th Rifle Division (Bikin) – Col. Fyodor Borisov

66th Rifle Division (Lesozavodsk) – Col. Mikhail Yushkevich

69th Rifle Division (Blagoveshchensk) – Kombrig Afanasy Shemenkov

Transbaikal Front

Kombrig Vsevolod Yakovlev.

Komdiv Pyotr Korytnikov.

CO: Kombrig Vsevolod Yakovlev

Headquarters: Chita

17th Army

CO: Komdiv Pyotr Korytnikov

HQ: Chita

57th Corps (Öndörkhaan and Bayan Tümen)

CO: Komdiv Nikolai Feklenko

Strength: 25,809 men, 392 tanks, 335 armored cars.

36th Motorized Rifle Division

57th Rifle Division

93rd Rifle Division

7th Motorized Tank Brigade (96 armoured cars)

8th Motorized Tank Brigade (36 BT-5, 8 T-37A, 96 armoured cars)

9th Motorized Tank Brigade (96 armoured cars)

11th Tank Brigade (115 BT-5 and BT-7, 10 T-26, 1 T-37, 41 armoured cars)

33rd Chemical Tank Brigade (178 T-26, 19 OT-26 flamethrower tanks, 10 BT-5, 24 T-37, 1 OT-37 flamethrower tank, 6 armoured cars)

Front Reserve

114th Rifle Division

152nd Rifle Division

Transbaikal Fortified Region

Soviet Pacific Fleet

Flag Officer, 2nd Rank Nikolai Kuznetsov.

Home Base: Vladivostok

CO: Flag Officer, 2nd Rank Nikolai Kuznetsov

Destroyers (2)

Voikov (Orfey-class destroyer)

Stalin (Orfey-class destroyer)

Guard ships (3)

Metel' (Uragan-class guard ship)

V'yuga (Uragan-class guard ship)

Zarnitsa (Uragan-class guard ship)

Submarines (60)

32 Shchuka-class submarines

22 M-class submarines

6 Leninets-class submarines

Minesweepers (8)

8 Fugas-class minesweepers

Mongolian People's Army

Khorloogiin Choibalsan.

CO: Marshal Khorloogiin Choibalsan

Headquarters: Ulaanbaatar

1st Cavalry Division

2nd Cavalry Division

3rd Cavalry Division

4th Cavalry Division

5th Cavalry Division

6th Cavalry Division

7th Cavalry Division

8th Cavalry Division

Campaign of 1940

Fall of Vladivostok

The Soviet 305 mm No. 981 "Voroshilovskaya" naval battery near Vladivostok destroyed by a Japanese air attack.

Soviet naval infantry in defensive positions north of Vladivostok.

Peace and aftermath

Tokyo Peace Treaty and the Soviet–Japanese Neutrality Pact

The Tokyo Peace Treaty was signed in Tokyo on 13 April 1941 by Foreign Minister Yosuke Matsuoka and Ambassador Yoshitsugu Tatekawa for Japan and Foreign Minister Maxim Litvinov for the Soviet Union. With it, the Soviet Union ceded the port of Vladivostok and a portion of Primorye to Japan. On the same day, the same people also signed the Soviet–Japanese Neutrality Pact, in which the parties pledged to ensure the neutrality between the Soviet Union and the Empire of Japan. A similar declaration was also signed regarding the People's Republic of Mongolia and Manchukuo. The Soviet Union pledged to respect the territorial integrity and inviolability of Manchukuo, while Japan did the same for the Mongolian People's Republic.

Casualties

Soviet prisoners of war outside Vladivostok, May 1940.

Political consequences

Japan

The war played an important part in subsequent Japanese conduct in World War II. While Japan had taken control of Vladivostok inflicted a defeat on the Red Army, the Army lost prestige due to its failures in the Soviet–Japanese War and earned the Kwantung Army the displeasure of officials in Tokyo. The prolonged fighting and heavy losses and the military setbacks on the Mongolian front, combined with the Chinese resistance in the Second Sino-Japanese War and negative Western attitudes towards Japanese expansionist tendencies, moved the Imperial General Staff in Tokyo away from the policy of the North Strike Group favored by the Army, which wanted to seize Siberia for its resources as far as Lake Baikal.

Instead, support shifted to the South Strike Group (Nanshin-ron), favored by the Navy, which wanted to procure the colonial resources of Southeast Asia, especially the petroleum and mineral-rich Dutch East Indies, and to neutralize the threat posed by Western military forces in the Pacific. In an effort to discourage Japanese rising militarism and expansionism, Western powers including Australia, the United States, Britain, and the Dutch government in exile, which controlled the petroleum-rich Dutch East Indies, imposed an oil, iron ore, and steel embargo on Japan, denying it the raw materials needed to continue its activities in China and French Indochina. In Japan, the government and nationalists viewed these embargoes as acts of aggression; imported oil made up about 80% of domestic consumption, without which Japan's economy, let alone its military, would grind to a halt. The Japanese media, influenced by military propagandists, began to refer to the embargoes as the "ABCD ("American-British-Chinese-Dutch") encirclement" or "ABCD line". Faced with a choice between economic collapse and withdrawal from its recent conquests (with its attendant loss of face), the Japanese Imperial General Headquarters (GHQ) began planning for a war with the Western powers in April or May 1941.

Soviet Union

The Soviet defeat was met with shock in the West and across the Far East. The Soviet Union lost virtually its entire Pacific Fleet, and also much international esteem. This was particularly true in the eyes of Nazi Germany. By ceding Vladivostok to Japan, the Soviet Union lost their largest port on the Pacific Ocean, and the chief economic and political center in the Far East. Due to the Great Purge of 1936–1938 the Red Army had lost many competent and experienced military officers, leaving the Red Army with a relatively inexperienced leadership. As a result of military incompetence and inexperience, the Soviet Union suffered heavy losses in men and materiel. The Red Army had been humiliated, as Soviet propaganda was working hard to explain the failures of the Soviet military to the populace. The Soviet General Staff Supreme Command (Stavka) met in September 1940, reviewed the lessons of the Polish campaign and the war against Japan, and recommended reforms. The role of frontline political commissars was reduced and old-fashioned ranks and forms of discipline were reintroduced. Equipment and tactics were improved. The reforms, however, were delayed and not completed until 1942 due to the ongoing war against Nazi Germany and their European Allies.

The war was the first victory for the soon-to-be-famous Soviet general Georgy Zhukov, earning him the first of his four Hero of the Soviet Union awards, while Ivan Konev also was commended for his service. On the other hand, two other generals, Grigoriy Shtern and Yakov Smushkevich, were executed in the 1940 Purges. Both Zhukov and Konev were promoted and transferred to the west. In 1942, Zhukov planned and executed the Red Army's offensive at the Battle of Stalingrad, using a technique very similar to his strategy on the Mongolian front, in which the Soviet forces held the enemy fixed in the center, built up an undetected mass force in the immediate rear area, and launched a pincer attack on the wings to trap the German army.

The subsequent negotiation of the Treaty of Tokyo and the Soviet–Japanese Neutrality Pact secured the Far East for the remainder of the Soviet-German War, which freed up forces and enabled the Soviets to concentrate on their war with Germany and the Japanese to concentrate on their southern expansion into Asia and the Pacific Ocean. However, the Red Army always remained cautious about the possibility of another, larger Japanese incursion as late as early 1944. In December 1943, when the American military mission proposed a logistics base be set up east of Lake Baikal, the Red Army authorities were according to Coox "shocked by the idea and literally turned white". Due to this caution, the Red Army kept a large force in the Far East even during the bleakest days of the war in Europe. For example, on 1 July 1942, Soviet forces in the Far East consisted of 1,200,000 troops, 8,750 artillery pieces, 1,800 tanks and self-propelled guns, and 2,600 combat aircraft. Despite this, the Soviet operations chief of the Far Eastern Front, General A. K. Kazakovtsev, was not confident in his army group's ability to stop an invasion if the Japanese committed to it (at least in 1941–1942), commenting: "If the Japanese enter the war on Hitler's side ... our cause is hopeless."

With success at the Battle of Stalingrad and the eventual defeat of Germany becoming increasingly certain, the Soviet attitude to Japan changed, both publicly, with Stalin making speeches denouncing Japan, and privately, with the Soviets building up forces and supplies in the Far East. At the Tehran Conference (November 1943), Stalin, Winston Churchill, and Franklin Roosevelt agreed that the Soviet Union would enter the war against Japan once Germany was defeated. Stalin faced a dilemma since he wanted to avoid a two-front war at almost any cost but also wanted to liberate Vladivostok and extract gains in the Far East as well as Europe. The only way that Stalin could make Far Eastern gains without a two-front war would be for Germany to surrender before Japan.

Nevertheless, even before the defeat of Germany, the Soviet buildup in the Far East had steadily accelerated. By early 1945, it had become apparent to the Japanese that the Soviets were preparing to invade Manchuria, but they were unlikely to attack prior to Germany's defeat. In addition to their problems in the Pacific, the Japanese realised that they needed to determine when and where a Soviet invasion would occur. At the Yalta Conference (February 1945), Stalin secured from Roosevelt the promise of Stalin's Far Eastern territorial desires in return for agreeing to enter the Pacific War within two or three months of the defeat of Germany. By mid-March 1945, things were not going well in the Pacific for the Japanese, who withdrew their elite troops from Manchuria to support actions in the Pacific. Meanwhile, the Soviets continued their Far Eastern buildup.

On 9 May 1945 (Moscow Time), Germany surrendered and so if the Soviets were to honour the Yalta Agreement, they would need to enter war with Japan by 9 August 1945. The situation continued to deteriorate for the Japanese, now the only Axis power left in the war. They were keen to remain at peace with the Soviets and extend the Neutrality Pact and also wanted to achieve an end to the war. Since Yalta, they had repeatedly approached or tried to approach the Soviets to extend the Neutrality Pact and to enlist the Soviets in negotiating peace with the Allies. In the closing months of World War II, the Soviet Union would annul the Neutrality Pact and invade the Japanese territories in Manchuria, northern Korea, and the southern part of Sakhalin island.

See also

• Far Eastern Front (WFAC)