The causes of World War Two can be divided into long term causes and short term causes. There can be little doubt that one of the long term causes of the war was the anger felt in Weimar Germany that was caused by the Treaty of Versailles. Another long term cause was the obvious inability of the League of Nations to deal with major international issues. In the 1930's these would have been in Manchuria and Abyssinia. In both conflicts the League showed that it was unable to control those powers that worked outside of accepted international law. In the case of Manchuria it was Japan and in Abyssinia it was Mussolini's Italy.
With such apparent weakness, Hitler must have known that at the very least he could push the boundaries and see what he could get away with. His first major transgression was his defiance of the Versailles Treaty when he introduced re-armament into Nazi Germany. The expansion of all three arms of the military was forbidden by treaty. Hitler, however, ignored these restrictions. The world's powers did nothing. The same occurred in 1936 when Nazi Germany re-occupied the Rhineland. Forbidden by Versailles, Hitler felt confident enough to ignore it. Europe's failure to react was also demonstrated when Austria and the Sudentenland were occupied. Only when it became obvious that Hitler was determined to expand east and that what was left of Czechoslovakia and region Poland were to be his next targets, did the major powers of Europe react. Hitler's reference to the Munich Agreement as a “scrap of paper” made clear his intentions. However, in 1938, very many in the UK had supported Neville Chamberlain's attempts at avoiding war (appeasement) and public opinion was on his side. This only changed when it became clear that appeasement had failed and the public rallied to the side of Winston Churchill - the man who had insisted that Chamberlain had taken the wrong course of action.