Most historians consider the war began on September 1, 1939, with the invasion of Poland by Germany, which has attracted a conflict France, Britain and the Commonwealth. Some historians believe that attacking China to Japan (July 7, 1937) marks the beginning of world conflict. Soviet Union had annexed the eastern part of Poland in 1939 triggered a war with Finland separately and was attacked by Nazi Germany in June 1941. United States entered the conflict in December 1941, after the attack on Pearl Harbor. The war ended in 1945, when all the Axis powers were defeated.
The main theaters of war were the Atlantic Ocean, Western and Eastern Europe, Mediterranean, North Africa, Middle East, Asia Pacific and South-East and China. In Europe, the war ended with the unconditional surrender of Nazi Germany on May 8, 1945, but continued in Asia until Japan's surrender – August 15, 1945.
Postwar Europe was divided between Western and Soviet spheres of influence. If the West went to war reconstruction through the Marshall Plan, Eastern European countries became Soviet satellite states, adopting methods planned economy and totalitarian one-party politics. This division was informal. In fact, there were no formal arrangements for the division of spheres of influence, relations between the victors in war have become increasingly strained military lines of demarcation became the de facto borders eventually countries. Western European countries have become largely, members of NATO, while most of the countries of Eastern Europe were the Warsaw Pact ally, these two military-political alliances that have fueled the Cold War.