Causes of World War II

The causes of World War II have been given considerable attention by historians. The immediate precipitating event was the invasion of Poland by Nazi Germany on September 1, 1939, and the subsequent declarations of war on Germany made by Britain and France, but many other prior events have been suggested as ultimate causes. Primary themes in historical analysis of the war's origins include the political takeover of Germany in 1933 by Adolf Hitler and the Nazi Party; Japanese militarism against China, which led to the Japanese invasion of Manchuria and the Second Sino-Japanese War; Italian aggression against Ethiopia, which led to the Second Italo-Ethiopian War; the Soviet Union's desire to reconquer old territories of the Russian Empire, which led to the Soviet invasion of Poland, the Soviet occupation of Bessarabia and Northern Bukovina, the occupation of the Baltic states and the Winter War.

During the interwar period, deep anger arose in the Weimar Republic over the conditions of the 1919 Treaty of Versailles, which punished Germany for its role in World War I with heavy financial reparations and severe limitations on its military that were intended to prevent it from becoming a military power again. The demilitarisation of the Rhineland, the prohibition of German unification with Austria, and the loss of its overseas colonies as well as some 12% of its pre-war land area and population all provoked strong currents of revanchism in German politics.

During the worldwide economic crisis of the Great Depression in the 1930s, many people lost faith in liberal democracy and countries across the world turned to authoritarian regimes.^[1] In Germany, resentment over the terms of the Treaty of Versailles was intensified by the instability of the German political system, as many on both the Right and the Left rejected the Weimar Republic liberalism. The most extreme political aspirant to emerge from that situation was Adolf Hitler, the leader of the Nazi Party. The Nazis took totalitarian power in Germany from 1933 and demanded the undoing of the Versailles provisions. Their ambitious and aggressive domestic and foreign policies reflected their ideologies of antisemitism, unification of all Germans, the acquisition of "living space" (Lebensraum) for agrarian settlers, the elimination of Bolshevism and the hegemony of an "Aryan"/"Nordic" master race over "subhumans" (Untermenschen) such as Jews and Slavs. Other factors leading to the war included the aggression by Fascist Italy against Ethiopia, militarism in Imperial Japan against China, and Military occupations by the Soviet Union.

At first, the aggressive moves met with only feeble and ineffectual policies of appeasement from the other major world powers. The League of Nations proved helpless, especially regarding China and Ethiopia. A decisive proximate event was the 1938 Munich Conference, which formally approved Germany's annexation of the Sudetenland from Czechoslovakia. Hitler promised it was his last territorial claim, nevertheless in early 1939, he became even more aggressive, and European governments finally realised that appeasement would not guarantee peace but by then it was too late.

Britain and France rejected diplomatic efforts to form a military alliance with the Soviet Union, and Hitler instead offered Stalin a better deal in the Molotov–Ribbentrop Pact of August 1939. An alliance formed by Germany, Italy, and Japan led to the establishment of the Axis powers.