The correct answer is: "Yalta Conference".
The Yalta Conference was celebrated in 1945 and gathered the main leaders of the Allied forces ( US, UK and the Soviet Union) that aimed to discuss the reorganization of Europe and specially of Germany after WWII.
In that moment, the nazis had been already expelled from Poland, and Churchill demanded the right of free elections for them. Stalin expressed his agreement on the demand, but he had actually installed a soviet-influenced goverment in the Polish territory that was in that moment occupied by the Red Army.