Why did WWI happen? Explain the spark and the M.A.I.N. causes. Do you think the war could have been prevented?

World War 2 Happened because of a number of reasons. German nationalism and anger over losing WW1, their economy. Japan's imperialistic adventures. America and their later allies usually doing nothing to prevent Germany from rising. America cut off Japan's oil supply and that made them a hella mad. Anti-communism was pretty rampant back then as it is today.