The powerful leader of the Soviet Union during World War II was Joseph Stalin. Rising to power in the late 1920s, Stalin transformed the Soviet Union into a totalitarian state and played a crucial role in the Allied victory against the Axis powers. His leadership was marked by significant industrialization and collectivization, but also severe repression and purges that eliminated perceived enemies. Stalin's military strategies and the Red Army's resilience, especially during battles like Stalingrad, were pivotal. Post-war, his authority established the USSR as a major world superpower, significantly influencing global politics during the Cold War.