The Imperial Japanese Navy launches a surprise attack on the US naval base at Pearl Harbor, Hawaii, bringing the United States into World War II.
Japanese forces attack Lạng Sơn and land near Haiphong, compelling the French administration to accept Japanese bases in Tonkin.
British forces in Singapore surrender to Japan, the largest capitulation in British military history, beginning the Japanese occupation of Malaya.
Soviet and Mongolian forces under Georgy Zhukov defeat the Japanese on the Mongolian–Manchurian border.
Germany invades Poland, starting the deadliest conflict in human history, which ends with Japan's formal surrender on 2 September 1945.
Allied forces carry out the largest seaborne invasion in history on the Normandy coast, opening a Western Front to liberate Western Europe.
A clash between Japanese and Chinese troops near Beijing begins the full-scale Second Sino-Japanese War (1937–1945).