During World War II
- In September 1940, Japan signed the Tripartite Pact with Nazi Germany and Fascist Italy, in which they agreed to assist one another should any of them be attacked by a country not already involved in the war. Japan had legitimate beef towards Britain and particularly America; these included Western refusal to accept Asians as equal to Europeans and North Americans, restraints on Japanese trade, unwillingness to allow the Japanese the same kind freedom in Manchuria that Americans and British regularly took for themselves in Latin America and throughout the British empire, and the United States' insulting policies toward Japanese immigration.
- Because after World War I they received little for aiding the allied countries, They decide that they could claim the land they needed if they helped the axis. It was a chance to expand.
- Japan sent troops to occupy French Indochina that same month, and the United States responded with economic sanctions, including an embargo on oil and steel. A little over a year later, Hirohito consented to the decision of his government to battle the Americans. On December 7, 1941, Japanese planes bombared the U.S. naval base at Pearl Harbor near Honolulu, Hawaii, destroying or crippling is ships and killing almost 2,500 men.