The countries that fought in World War II were Germany, Italy and Japan, which comprised the Axis Powers, and Britain, France, Australia, Canada, New Zealand, India, the Soviet Union, China and the United States of America, which comprised the Allies. Although Ireland remained neutral, many Irish fought on the side of the Allies. This war was fought for dominance over Europe, Asia and the Pacific.
World War II began when Germany invaded Poland on Sept. 1, 1939. Scholars estimate that there were 50 to 60 million casualties, mostly civilians, during the war. It was the largest-scale conflict in history and spanned nearly every continent.
American involvement began in November 1939, when Congress, at the behest of president Franklin Roosevelt, repealed an arms embargo preventing it from selling arms to foreign countries. By June of 1940, The United States began a major effort to build military power, and it began the Lend-Lease practice to aid Great Britain, which stood alone at that time. The United States fully committed immediately following the bombing of Pearl Harbor by Japan on Dec. 7, 1941. The end results of World War II included ushering in the nuclear age, the founding of the United Nations, the end of the Great Depression, and strong advancements for civil rights for African Americans and women.