What was the main cause of World War II?

World War II began when Britain and France declared war on Germany in September 1939 after Germany's invasion of Poland. Though the invasion of Poland was what ultimately caused the outbreak of World War II, there are many other major factors that contributed to this war.

The earliest beginnings of World War II can be traced back to the Treaty of Versailles, which Germany was forced to accept after World War I. Among other things, this treaty caused Germany to accept the blame for starting World War I. This resulted in Germany needing to significantly reduce the size of its military and pay 6.6 million pounds for the damage the war caused.

The German people felt the treaty was too harsh, and the country suffered through extreme poverty in the 1920s. Dissatisfied with their government, the German people voted Adolf Hitler as Chancellor in 1933. Hitler quickly began to reestablish the military and promised the German people to restore the country to greatness. This led to Germany invading other countries, which ultimately led to World War II.