What country joined the Allies in 1941?

In 1941, the Soviet Union officially joined the Allies following the German invasion known as Operation Barbarossa, which began on June 22, 1941. Initially, the USSR had a non-aggression pact with Germany, but the invasion forced them to align with the Allied powers against Axis forces. This marked a significant shift in the dynamics of World War II, as the Soviet Union played a crucial role in the eventual defeat of Nazi Germany.