"Russian dictator during World War II. He was infamous for his brutality before, during and after the War." Joseph Stalin, the Soviet Union's leader during World War II (called the Great Patriotic War by the Soviets), came to power after the death of Vladimir Lenin in 1924. He was a harsh and brutal tyrant. In 1937-38, he purged his military of many of its best officers. The purge also extended to the intelligentsia. This act deprived him of many competent leaders in World War II. In 1939, Stalin and Adolf Hitler signed the Nazi-Soviet Non-aggression Treaty that divided Poland between Germany and the Soviet Union, as well as pledging non-aggression between the signatories. When the Germans launched their invasion of the Soviet Union (Operation Barbarossa) in 1941, Josef Stalin was caught completely off guard and had a nervous breakdown. However, he recovered and was able to rally his country in an effort to stop the Germans. The Germans had advanced to the very outskirts of Moscow, before being stopped by a stubborn Russian defense. In 1942, Stalin issued Order 227, which forbade the giving of any more ground to the advancing German forces. This order, like the purges, cost the Soviets a great number of men. America, Britain and others provided aid in the form of tanks, planes, ships, foodstuffs, and other war material to the Soviets. Stalin met with President Roosevelt and Winston Churchill, whom he did not trust, at Teheran and Yalta and with President Harry Truman and Clement Attlee at Postdam in 1945. After the war in Europe ended, Stalin continued his brutal purges, killing anyone he perceived as an opponent, both in Russia and Eastern Europe. He precipitated the beginning of the Cold War, which would last until the 1990s. Stalin died of natural causes in 1953.