Germany and Japan were directly responsible for WW2.
According to the terms of the Treaty of Versailles, Germany was not permitted to have an army larger than 100,000. In the early 1930's Germany secretly started rebuilding her armed forces in anticipation of war. Germany could not of even considered attacking Poland and France if her armed forces were still at 100,000 men. WW2, as we know it, would never of happened had Germany not been able to rebuild their armed forces.
While Germany was rebuilding in the early 30's , Japan was attacking China and trying to conquer and enslave the Chinese people. That's why America put an oil embargo on Japan. Once America embargoed Japan, they decided to invade Southeast Asia and Indonesia to steal the oil they needed and enslave those people.
When they went to Asia and Indonesia, they had to attack Pearl Harbor to keep the American Pacific Fleet from helping those countries.