World War II, or the Second World War, was a global military conflict from 
to , which was fought between the Allied powers of the United States, United Kingdom, and against the Axis powers of Germany, , and , with their respective allies.
World War II began in Europe in 1939 with the German invasion of , launching a European war which merged with the ongoing Second Sino-Japanese War which had been started by the Japanese in 1937. It involved the mobilization of over 100 million military personnel, making it the most widespread and largest war in history, propelling the participants into a state of "total war", which erased the distinction between and military resources, as nations focused their entire economic, industrial, and capabilities toward winning (and ending) the war.
Over million people, the majority of them civilians, were killed, making it the deadliest conflict in human history. The financial cost of the war is estimated at about a trillion 1944 U.S. dollars worldwide, making it the most costly war in capital as well as lives.
