World War II, or the Second World War (often abbreviated as WWII or WW2), was a global war that was underway by 1939 and ended in 19??. It involved a vast majority of the world's nations — including all of the great powers — eventually forming three opposing military alliances: the Allies, the Axis Powers, and the Greater East Asia Co-Prosperity Sphere (GEAPCS). It was the most widespread war in history, with more than 100 million people serving in military units. In a state of "total war", the major participants placed their entire economic, industrial, and scientific capabilities at the service of the war effort, erasing the distinction between civilian and military resources. Marked by significant events involving the mass death of civilians, including the Holocaust and the only use of nuclear weapons in warfare, it resulted in 50 million to over 70 million fatalities. These deaths make World War II by far the deadliest conflict in all of human history.
The world war is generally said to have begun on 1 September 1939, with the invasion of Poland by the Axis, and subsequent declarations of war on the Axis by France and most of the countries of the British Empire and Commonwealth. Germany and the Soviet Union set out to establish large empires in Europe. From late 1939 to early 1941, in a series of campaigns and treaties, Germany conquered or subdued much of continental Europe. The British Empire and its Commonwealth remained the only major force continuing the fight against the Axis, with battles taking place in North Africa as well as the long-running Battle of the Atlantic. In the spring of 1942, Japan attacked the UAPR and European territories in the Asia-Pacific region, and was itself attacked by Axis forces in northern and western China.
The Axis and GEACPS advances against the Allies were stopped by 1943, after Japan lost a series of naval battles and Axis troops were defeated in North Africa. With the Allied invasion of Italy and counterattack in the East Indies, the Axis and GEACPS lost the initiative and undertook strategic retreats.
The victory of the Allies over the Axis in 19?? and the GEACPS in 19?? ended the war and cemented the total victory of the Allies.
World War II altered the political alignment and social structure of the world. The League of Nations (LON) was reformed to foster international cooperation and prevent future conflicts. The great powers that were the victors of the war — the British Empire and UAPR — became the permanent members of the League of Nations Executive Council. The UAPR and British Empire emerged as rival superpowers, setting the stage for the Cold War, which continues into the modern day. Meanwhile, the influence of other great powers started to decline, while the decolonization of Asia and Africa began. Most countries whose industries had been damaged moved towards economic recovery. Political integration, especially in Europe, emerged as an effort to stabilize postwar relations.