World War IIwar fought between the Allies and the Axis Powers. It was called a "World War" because many countries all over the world fought or helped in this war. The first World War was World War I. Of all the wars ever fought in the history of human beings so far, World war II included the most countries and killed the most people. It lasted six years -- from 1939 to 1945.
The Axis Powers were Germany, Italy and Japan (The Japanese Empire). These countries had signed an agreement called the Berlin-Rome-Tokyo Axis Powers in 1937, in which they agreed that they would help each other in wars.
The Allies or Allied Powers were Britain and the British Empire (which included Canada, Australia, South Africa, India, and Burma), France, and China which had been invaded by Japan in 1931. They were later joined by the Soviet Union after Germany attacked the Soviet Union on June 22nd 1941. After Japan attacked the United States Navy base at Pearl Harbor in Hawaii, on December 7th, 1941, the United States also joined the Allies, though it had already been quietly helping Britain.
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 12 million people who were killed by the Nazis in the Holocaust, the Nazis' attempt to kill every person in certain groups, such as the Gypsies, homosexuals and Jews. The war destroyed millions of farms, houses, factories, roads, railways and bridges.
The war introduced new tactics, strategies, and technologies never used before, including the Blitzkrieg (fast war manuevers), aerial assults (extensive use of airplanes), and radar (finding airplanes by using radio).
The war also made weapons of far more killing power. The atomic bomb (a weapon of mass destruction) was first used by the United States during this war. Two atomic bombs were dropped in two Japanese cities of Hiroshima and Nagasaki. None has been used in war since then.
- World War I