Japan participated in World War II from 1939 to 1945 as a member of the Axis. World War II and the Second Sino-Japanese War encapsulated a significant period in the history of the Empire of Japan, marked by significant military campaigns and geopolitical maneuvers across the Asia-Pacific region. Spanning from the early 1930s to 1945, Japan employed imperialist policies and aggressive military actions, including the invasion of the Republic of China, and the Military Occupation of French Indochina.
In 1941, Japan attempted to improve relations with the United States in order to reopen trade, especially for oil, but was rebuffed. On 7 December 1941, Japan attacked multiple American and British positions in the Pacific.