World War II, or the Second World War, was a global military conflict. It was started from the joining of what had initially been two separate conflicts. The first began in Asia in 1937 as the Second Sino-Japanese War. The other began in Europe in 1939 with the German invasion of Poland. This global conflict split the majority of the world's nations into two opposing military alliances. One was called the Allies. The other was called the Axis powers. It involved the mobilization of over 100 million military personnel. Thi makes it the most widespread war in history. It placed the participants in a state of total war. That erased the distinction between civil and military resources. This resulted in the complete activation of a nation's economic, industrial, and scientific capabilities for the purposes of the war effort. Over 60 million people, the majority of them civilians, were killed. It is the deadliest conflict in human history. The Allies were victorious and the United States and Soviet Union emerged as the world's two leading superpowers.