Poland had apparently lain dormant under the Nazi heel for nearly five years, suffering the waves of genocidal round ups, organized looting and the brutal suppression of its culture. The Poles, however, had in fact formed an underground army, the Armia Krajowa (Home Army), and waited for the moment when German weakness would offer the opportunity for a successful rising. That moment seemed to have arrived in July 1944. As the Soviet armies began to advance into eastern Poland following the destruction of the German Army Group Centre in the successful Bagration offensive, the AK launched its revolt in Warsaw on August 1, 1944. Though its 5,000 fighters achieved some initial successes, the Germans were able to retain control over both the Vistula River bridges and the airbase, which ultimately doomed the revolt to isolation and defeat. The SS was put in charge of suppressing the rebellion, beginning another wave of atrocities, shocking even by Eastern Front standards.
By the beginning of September, it was clear that the rebellion was doomed. The Western Allies attempted to fly weapons and supplies to Warsaw, but their efforts were undermined by Stalin's unwillingness to provide airbases. Stalin himself waited until the rebellion was approaching its death throes before allowing the First Polish Army (part of the Red Army) to cross the Vistula River to aid the rebellion. Although these reinforcements succeeded in briefly establishing a link up, it was too late. The AK finally agreed to surrender on October 2.