I believe it was the use of poisonous gasses, which they not only used on the Jews but in war too......., or The newly created Machine gun<span />
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He grew Germany's military. The treaty didn't allow the German military to become over a certain size.
Answer:
The major causes of World War II were numerous. They include the impact of the Treaty of Versailles following WWI, the worldwide economic depression, failure of appeasement, the rise of militarism in Germany and Japan, and the failure of the League of Nations.
