Which countries were considered the major Allied Powers during World War II?

The major Allied Powers during World War II included the United States, Britain, and the Soviet Union (USSR) largely because they played significant roles in opposing the Axis Powers and contributed vastly to the war effort with military resources, manpower, and economic support.

The United States provided unparalleled industrial capability and military strength, entering the war after the attack on Pearl Harbor in 1941 and leading crucial campaigns in both the European and Pacific theaters. Britain was one of the earliest opponents of the Axis Powers, enduring the Battle of Britain and leading efforts to resist Nazi Germany. The Soviet Union, initially under a non-aggression pact with Germany, joined the Allies after Germany invaded in 1941 and became a pivotal force on the Eastern Front, culminating in significant victories that turned the tide of the war.

While other countries like France, Canada, Australia, India, China, and Brazil contributed to the Allied efforts, they were not considered the primary powers in the same way as the United States, Britain, and the USSR, who formed the backbone of the Allies and coordinated major military strategies that ultimately led to victory in 1945.