The Warsaw Uprising by the Polish resistance Home Army in August 1944 occurred as the Russian Army approached the city and the Germans were retreating. Unfortunately, the Russian advance stopped short of the city, leaving the Poles (who assumed the Russians would join in the battle) to stand alone against vastly superior German forces for two months. The Germans defeated the Poles and demolished the city before the Russian advance continued.
- Soviet hostility to the Polish government in exile in the wake of the 1940 Katyn Massacre of Polish nationals carried out by the Russian NKVD
- Soviet refusal to allow Allied planes on missions to Warsaw to land on its airfields
- The Teheran Conference agreement reached between Roosevelt, Churchill and Stalin that placed Poland within the Soviet sphere of influence