World War II was a global war from 1939 to 1945 that involved over 30 countries. The major Allied powers were Britain, the United States, and the Soviet Union, led by Winston Churchill, Franklin Roosevelt, and Joseph Stalin respectively. The major Axis powers were Germany, Italy, and Japan, led by Adolf Hitler, Benito Mussolini, and Emperor Hirohito respectively. Some key battles included the Battle of France in 1940, the Battle of Stalingrad from 1942 to 1943, and the Battle of Berlin from 1945. World War II resulted in millions of casualties and the collapse of the Nazi party in Germany and the Japanese and Italian empires.