Answer: Invading other countries to add territory.
Step-by-step explanation:
Some of the main causes of World War II were the 1930s aggressive Nazi foreign policy, Italian Fascism invasion or Ethiopia, and the Japanese militarism and invasion of China.
Italy stated a claim over Ethiopia and invaded it in 1935. In 1931 Japan had built a dependent state in Manchuria and grew beyond in China from 1937.
Germany systematically mocked the Versailles treaty, secretly starting re-armament, remilitarizing the Rhineland in 1936, annexing Austria and the Sudetenland in 1938.