Learn about Japan's pre-World War II invasions, joining of the Axis powers, and attack on Pearl Harbor In September 1940 Imperial Japan signed the Tripartite Pact with Nazi Germany and fascist Italy. This alliance gave Japanese leaders the security they needed to expand their designs for an East Asian empire into Indochina and beyond.

By 1939, the situation was clear to the Japanese, and it grew worse when the Chinese Communists saw the advantages of establishing “liberated zones” behind Japanese positions. American aid allowed a slow buildup of an organized Chinese Army.

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 encapsulate a significant period in the history of the Empire of Japan, marked by significant military campaigns and geopolitical maneuvers across the Asia-Pacific region.

Events in the year 1939 in Japan. It corresponds to Shōwa 14 (昭和14年) in the Japanese calendar.

World War II - Pacific, Japan, Allies: Overt hostilities between Japan and China began after the Marco Polo Bridge incident of July 7, 1937, when shots were exchanged between Chinese and Japanese troops on the outskirts of Peking.