Answer:
The main reason why WW2 happened was because Japan attacked usa on pearl harbor and usa declared war.
Step-by-step explanation:
some events:
-12/7/1941:Pearl Harbor
-12/11/1941:Usa declares war.
Answer: 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.
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