Warsaw Uprising - Wikipedia

On October 2, 1944, Polish resistance fighters capitulated in the Warsaw Uprising, with some 250,000 people killed. From the article:

"The Uprising began on 1 August 1944 as part of a nationwide Operation Tempest, launched at the time of the Soviet Lublin–Brest Offensive. The main Polish objectives were to drive the Germans out of Warsaw while helping the Allies defeat Germany. An additional, political goal of the Polish Underground State was to liberate Poland's capital and assert Polish sovereignty before the Soviet-backed Polish Committee of National Liberation could assume control. Other immediate causes included a threat of mass German round-ups of able-bodied Poles for "evacuation"; calls by Radio Moscow's Polish Service for uprising; and an emotional Polish desire for justice and revenge against the enemy after five years of German occupation.[13][14]

Initially, the Poles established control over most of central Warsaw, but the Soviets ignored Polish attempts to maintain radio contact with them and did not advance beyond the city limits. Intense street fighting between the Germans and Poles continued. By 14 September, the eastern bank of the Vistula River opposite the Polish resistance positions was taken over by the Polish troops fighting under the Soviet command; 1,200 men made it across the river, but they were not reinforced by the Red Army. This, and the lack of air support from the Soviet base five-minute flying time away, led to allegations that Joseph Stalin tactically halted his forces to let the operation fail, and to allow the Polish resistance to be crushed. Arthur Koestler called the Soviet attitude "one of the major infamies of this war which will rank for the future historian on the same ethical level with Lidice."[15]

Winston Churchill pleaded with Stalin and Franklin D. Roosevelt to help Britain's Polish allies, to no avail.[16] Then, without Soviet air clearance, Churchill sent over 200 low-level supply drops by the Royal Air Force, the South African Air Force, and the Polish Air Force under British High Command, in an operation known as the Warsaw Airlift. Later, after gaining Soviet air clearance, the U.S. Army Air Force sent one high-level mass airdrop as part of Operation Frantic.

Although the exact number of casualties remains unknown, it is estimated that about 16,000 members of the Polish resistance were killed and about 6,000 badly wounded. In addition, between 150,000 and 200,000 Polish civilians died, mostly from mass executions. Jews being harboured by Poles were exposed by German house-to-house clearances and mass evictions of entire neighbourhoods. German casualties totalled over 8,000 soldiers killed and missing, and 9,000 wounded. During the urban combat approximately 25% of Warsaw's buildings were destroyed. Following the surrender of Polish forces, German troops systematically levelled another 35% of the city block by block. Together with earlier damage suffered in the 1939 invasion of Poland and the Warsaw Ghetto Uprising in 1943, over 85% of the city was destroyed by January 1945, when the course of the events in the Eastern Front forced the Germans to abandon the city."