World War II (WWII or WW2), also known as the Second World War (after the recent Great War), was a global war that lasted from 1939 to 1945, though related conflicts began earlier. It involved the vast majority of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis. It was the most widespread war in history, and directly involved more than 100 million people from over 30 countries. In a state of "total war", the major participants threw their entire economic, industrial, and scientific capabilities behind the war effort, erasing the distinction between civilian and military resources. Marked by mass deaths of civilians, including the Holocaust (during which approximately 11 million people were killed)[1][2] and the strategic bombing of industrial and population centres (during which approximately one million people were killed, including the use of two nuclear weapons in combat),[3] it resulted in an estimated 50 million to 85 million fatalities. These made World War II the deadliest conflict in human history.[4]
The Empire of Japan aimed to dominate Asia and the Pacific and was already at war with the Republic of China in 1937,[5] but the world war is generally said to have begun on 1 September 1939[6] with the invasion of Poland by Germany and subsequent declarations of war on Germany by France and the United Kingdom. From late 1939 to early 1941, in a series of campaigns and treaties, Germany conquered or controlled much of continental Europe, and formed the Axis alliance with Italy and Japan. Following the Molotov–Ribbentrop Pact, Germany and the Soviet Union partitioned and annexed territories of their European neighbours, Poland, Finland, Romania and the Baltic states. The United Kingdom and the British Commonwealth were the only Allied forces continuing the fight against the European Axis powers, with campaigns in North Africa and the Horn of Africa as well as the long-running...