With the Soviet armies advancing from the east and driving out the German occupiers, the Polish nationalists seized their chance to liberate Warsaw. Operation Tempest, the largest single resistance action of World War II, began on 1 August with the Poles quickly taking control of much of the city centre and briefly establishing a bridgehead across the River Vistula. But Stalin then halted the Soviet advance at the city’s suburbs, refused contact with the rebels, withheld air support, and allowed the Germans to quell the uprising, resulting in their systematic destruction of much of the city. It is estimated that 17,000 Polish fighters were killed and over 200,000 civilians massacred in the ensuing two months of conflict, with all Jews being rounded up and murdered. Stalin at first ignored Churchill’s pleas for help, but later relented, allowing British and American airborne supply missions, but they came too late, and the Poles surrendered on 3 October. The Germans then largely demolished the remainder of the city.