Who started World War 2 and why?

World War 2 was started by Hitler when he invaded Poland in September 1939. France and Britain, who had guaranteed support to uphold Poland’s sovereignty, promptly declared war on Germany. 

The war was started because of Hitler’s desire to conquer Europe and create living space for Germans. Avenging the humiliating Versailles treaty was also an additional motivation to start World War II.

For further reading check the following articles:

• World War I
• World War II
• Causes of World War I