* Increasing its military spending and developing new weapons systems. Japan's military spending increased dramatically in the late 1930s and early 1940s. This build-up was seen as a threat by other countries in the region.
* Occupying Manchuria and other territories in Asia. Japan began to occupy territories in Asia in the 1930s and 1940s. These occupations were often brutal and oppressive, and they further increased tensions with other countries in the region.
* Forming an alliance with Germany and Italy. Japan formed an alliance with Germany and Italy in 1940. This alliance, known as the Axis Powers, was seen as a threat to the Allied Powers, which included the United States, Great Britain, and the Soviet Union.
* Attacking Pearl Harbor and other American targets. Japan's attack on Pearl Harbor in 1941 was the catalyst for the United States' entry into World War II. This attack, and other attacks on American targets, led to the eventual defeat of Japan and the end of World War II.