World War II
World War II was a war fought between the Allies (including Britain and the British Empire including Canada and Australia), France, Soviet Union - attacked by the German land and air forces on June 22nd 1941, United States - attacked by the Japanese Navy on December 7th, 1941 (Pearl Harbour) though it had already entered unofficially assisting Britain, China - which had been invaded by Japan in 1931, and many others) and the Axis Powers (Germany, Italy and Japan). World War II was the bloodiest war ever fought in the history of mankind so far. It lasted six years -- from 1939 to 1945.The war started on September 1, 1939, when Nazi Germany invaded Poland, and ended on August 15, 1945, after the unconditional (total) surrender of the Empire of Japan. About 50 million people were killed, including 6 million Jews who were killed by Nazis in the Holocaust (mass murder of the Jews), many Gypsies, homosexuals and others the Nazis hated.
The war introduced new technologies and stratgies never before seen in war, including the Blitzkreg (war manuevers), aerial assults (extensive use of airplanes), and radar (technology to detect airplanes). The war also made weapons of far more killing power. The atomic bomb (a weapon of mass destruction) was first introduced by the Americans during the war. Two atomic bombs were dropped in two Japanese cities of Hiroshima and Nagasaki. Thankfully none has been used in war since then.