Why did Japan join WW2?

As an island nation Japan faced shortages in oil and natural resources. Its imperial expansions in China had resulted in an oil embargo imposed by the United States. Therefore Japan’s leaders were consumed with the desire of replacing the United States as the dominant power of the Pacific.

Japan decided to attack the United States and British forces in Asia and seize the resources of Southeast Asia. To this end Jaan desired to create the “Greater Asia Co-Prosperity Sphere”, which was a euphemism for a colonial empire where resources were to be extracted from Japanese holdings in Manchuria, Korea, and North China.

For further reading check the following articles:

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