Answer:
Atomic weapons
Explanation:
Japanese expansion in East Asia began in 1931 with the invasion of Manchuria and continued in 1937 with a brutal attack on China. On September 27, 1940, Japan signed the Tripartite Pact with Germany and Italy, thus entering the military alliance known as the "Axis." Seeking to curb Japanese aggression and force a withdrawal of Japanese forces from Manchuria and China, the United States imposed economic sanctions on Japan. Faced with severe shortages of oil and other natural resources and driven by the ambition to displace the United States as the dominant Pacific power, Japan decided to attack the United States and British forces in Asia and seize the resources of Southeast Asia. Japan launched a surprise attack on the United States Pacific fleet at Pearl Harbor, Hawaii, on December 7, 1941. The attack severely damaged the American fleet and prevented, at least for the short term, serious American interference with Japanese military operations. In response, the United States declared war on Japan. Following Germany's declaration of war on the United States, the United States also declared war on Germany..
