World War II (Engine of Progress)

World War II, or the Second World War (often abbreviated WWII or WW2), was a global military conflict which involved a majority of the world's nations, including all great powers, organized into two opposing military alliances: the Allies and the Axis. The war involved the mobilization of over 100 million military personnel, making it the most widespread war in history. In a state of "total war", the major participants placed their entire economic, industrial, and scientific capabilities at the service of the war effort, erasing the distinction between civilian and military resources. Over fifty million people, the majority of whom were civilians, were killed, making it the deadliest conflict in human history.

The start of the war is generally held to be September 1, 1939, with the German invasion of Poland and subsequent declarations of war on Germany by most of the countries in the British Empire and Commonwealth, and by France. Subsequently, the Soviet Union invaded Poland from the east side. Many countries were already at war before this date, such as Ethiopia and Italy in the Second Italo-Abyssinian War and China and Japan in the Second Sino-Japanese War, and many who were not initially involved joined the war later, as a result of events such as the German invasion of the Soviet Union (Operation Barbarossa), and the attacks on Pearl Harbor and British colonies and subsequent declarations of war on Japan by Dutch and British Commonwealth.

In 1945 the war ended in a victory for the Allies. The Soviet Union and the United States subsequently emerged as the world's superpowers, setting the stage for the Cold War, which lasted for the next 40 years. The United Nations was formed in the hope of preventing another such conflict. The acceptance of the principle of self-determination accelerated decolonization movements in Asia and Africa, while Western Europe itself began moving toward integration.

Background
A variety of events led to the escalation of hostilities between the Axis and Allied powers prior to the start of the war. In the aftermath of World War I, a defeated Germany signed the Treaty of Versailles. This caused Germany to lose around 13% of its territory, stripped Germany of its colonies, prohibited German annexation of other states, imposed massive reparations and limited the size and makeup of Germany's armed forces. The Russian Civil War led to the creation of the Soviet Union which soon was under the control of Joseph Stalin. In Italy, Benito Mussolini seized power as a fascist dictator promising to create a "New Roman Empire." The Kuomintang (KMT) party in China launched a unification campaign against regional warlords and nominally unified China in the mid-1920s, but was soon embroiled in a civil war against its former Chinese communist allies. In 1931, an increasingly militaristic Japanese Empire, which had long sought influence in China as the first step of its right to rule Asia, used the Mukden Incident as justification to invade Manchuria; the two nations then fought several small conflicts, in Shanghai, Rehe and Hebei until the Tanggu Truce in 1933. Thereafter, Chinese volunteer forces continued the resistance to Japanese aggression in Manchuria, and Chahar and Suiyuan.

Adolf Hitler, after an unsuccessful attempt to overthrow the German government in 1923, became the Chancellor of Germany in 1933. He abolished democracy, espousing a radical, racially-motivated revision of the world order, and soon began a massive rearming campaign. This campaign worried France and the United Kingdom, who had lost much in the previous war, as well as Italy, which saw its territorial ambitions threatened by those of Germany. To secure its alliance, the French allowed Italy a free hand in Ethiopia, which Italy desired as a colonial possession. The situation was aggravated in early 1935 when the Saarland was legally reunited with Germany and Hitler repudiated the Treaty of Versailles, speeding up his rearmament program and introducing conscription. Hoping to contain Germany, the United Kingdom, France and Italy formed the Stresa Front. The Soviet Union, concerned due to Germany's goals of capturing vast areas of eastern Europe, concluded a treaty of mutual assistance with France.

Before taking effect though, the Franco-Soviet pact was required to go through the bureaucracy of the League of Nations, rendering it essentially toothless. In June 1935, the United Kingdom made an independent naval agreement with Germany easing prior restrictions. The United States, concerned with events in Europe and Asia, passed the Neutrality Act in August. In October, Italy invaded Ethiopia, with Germany the only major European nation supporting her invasion. Italy then revoked objections to Germany's goal of making Austria a satellite state.

In direct violation of the Versailles and Locarno treaties, Hitler remilitarized the Rhineland in March 1936. He received little response from other European powers. When the Spanish Civil War broke out in July, Hitler and Mussolini supported fascist Generalissimo Francisco Franco's nationalist forces in his civil war against the Soviet-supported Spanish Republic. Both sides used the conflict to test new weapons and methods of warfare, but the nationalists proved victorious in early 1939.

With tensions mounting, efforts to strengthen or consolidate power were made. In October, Germany and Italy formed the Rome-Berlin Axis and a month later Germany and Japan, each believing communism and the Soviet Union in particular to be a threat, signed the Anti-Comintern Pact, which Italy would join in the following year. In China, the Kuomintang and communist forces agreed on a ceasefire to present a united front to oppose Japan, this ceasefire would eventually culminate in the new constitutional convention in China that eventually led to China's evolution into an industrialized nation.

Chronology
The start of the war is generally held to be September 1, 1939 with the German invasion of Poland, although Britain and France entered two days later. Other dates for the beginning of war include the Japanese invasion of Manchuria on September 13, 1931, the start of the Second Sino-Japanese War on July 7, 1937, or one of several other events. Other's hold that there was a simultaneous Sino-Japanese War in East Asia, and a Second European War in Europe and her colonies, but they did not become a World War until they merged in 1941. Other important events that happened at the dawn of the war include the Second Italo-Abyssinian War between Ethiopia and Italy on October 1935 that led to the collapse of the League of Nations. Some have even gone so far as to state that WWI and WWII were really a single great conflict with a lengthy cease fire.

The end of the War also has several dates. Some sources state that it ended at the armistice of January 14, 1945, rather than the formal surrender of Germany (February 2, 1945).