The two dates most often mentioned as “the beginning of World War II” are July 7, 1937, when the “Marco Polo Bridge Incident” led to a prolonged war between Japan and China, and September 1, 1939, when Germany invaded Poland, which led Britain and France to declare war on Hitler's Nazi state in retaliation. read more
World War II Coming just two decades after the last great global conflict, the Second World War was the most widespread and deadliest war in history, involving more than 30 countries and resulting in more than 50 million military and civilian deaths (with some estimates as high as 85 million dead). read more
World War II, also called Second World War, conflict that involved virtually every part of the world during the years 1939–45. The principal belligerents were the Axis powers—Germany, Italy, and Japan—and the Allies—France, Great Britain, the United States, the Soviet Union, and, to a lesser extent, China. read more