The events of world war 2 were somewhat a consequence of Hitler, Chamberlain, Stalin, Mussolini, and the leaders of Imperial Japan, among others. These leaders of Japan sought a "retribution" against the Americans, for forcing Japan to open up once again to foreign trade, which led to the fall of the Tokugawa leadership in favor of the Meiji. They felt humiliated by a foreign power. They also sought new sources of timber, minerals and oil, outside of Japan. Stalin wanted to expand his totalitarian dominion. Mussolini and Hitler wanted absolute power, in the guise of lifting their respective nations out of economic collapse, restoring feelings of pride and glory, and creating empires and securing new oil supplies through conquest. A significant influence on Mussolini and Hitler was economic collapse in their countries, and their experiences as soldiers in the Great War. And the Great War was a consequence of technology of the time combined with old politics (Victorian, appropriate for the Napoleonic Era but not for the 20th century) and old ways of doing things.
So World War 2 was basically a consequence of changing politics, economics, and totalitarianism.
After the war, allied nations and the US helped create a more stable economic situation in Europe, and promote Democracy, though primarily against the spectre of communism. The Holocaust also had political repercussions, though carving a chunk out of Palestine for the Nation of Israel makes less sense to me than carving a chunk out of Germany (by the same argument used to create Israel, there would be parts of Lincoln in England, Lüneburg in Northwest Germany and possibly parts of France that I and my brother are the rightful owner of).
Oh, and Chamberlain was a fool. Easily manipulated by the Axis leaders, only took decisive action when forced too. A Weak Leader when Britain needed a Strong one. Churchill, Thank You.
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Life is Painful. Suffering is Optional. Keep your face to the Sun and never see your Shadow.