World War II, or the Second World War, was a global military conflict. The conflicts joined from 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 and Russian invasion of Poland. This global conflict split the majority of the world's nations into two opposing military alliances: the Allies and the Axis powers. It involved the mobilization of over 100 million military personnel, making it the most widespread war in history, and placed the participants in a state of "total war", erasing 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, making it the deadliest conflict in human history. The worldwide financial cost of the war is estimated at a trillion 1944 U.S. dollars, making it the most costly war both in capital expenditures as well as loss of lives.