World War 2

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, the Three Alls Policy, the strategic bombing of enemy industrial and/or population centers, and the first use of nuclear weapons in combat, it resulted in an estimated 50 million to 85 million fatalities. These made World War II the deadliest conflict in human history.

The Empire of Japan aimed to dominate East Asia and was already at war with the Republic of China in 1937, but the world war is generally said to have begun on 1 September 1939 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 formed the Axis alliance with Italy, conquering or subduing much of continental Europe. Following the Molotov–Ribbentrop Pact, Germany and the Soviet Union partitioned between themselves and annexed territories of their European neighbours, including Poland, Finland and the Baltic states. The United Kingdom and the other members of the British Commonwealth were the only major Allied forces continuing the fight against the Axis, with battles taking place in North Africa and the Horn of Africa as well as the long-running Battle of the Atlantic. In June 1941, the European Axis powers launched an invasion of the Soviet Union, giving a start to the largest land theatre of war in history, which tied down the major part of the Axis' military forces for the rest of the war. In December 1941, Japan joined the Axis, attacked the United States and European territories in the Pacific Ocean, and quickly conquered much of the Western Pacific.