The Allies had no intention of allowing Sikorski's successor, Stanisław Mikołajczyk, to threaten the alliance with the Soviets. No representative of the Polish government was invited to the Tehran Conference (28 November – 1 December 1943) or the Yalta Conference (4–11 February 1945), the two crucial events in which the Western Allies and the Soviet Union discussed the shape of the post-war world and decided on the fate of Poland. Only four months after Sikorski's death, in November 1943, at Tehran, Churchill and Roosevelt agreed with Stalin that the whole of Poland east of the Curzon Line would be ceded to the Soviets. In Teheran, neither Churchill nor Roosevelt objected to Stalin's suggestion that the Polish government in exile in London was not representing Polish interests; as historian Anita Prażmowska noted, "this spelled the end of that government's tenuous influence and raison d'être." After the Teheran Conference, Stalin decided to create his own puppet government for Poland, and a Committee of National Liberation (PKWN) was proclaimed in the summer of 1944. The committee was recognized by the Soviet Government as the only legitimate authority in Poland, while Mikołajczyk's Government in London, was termed by the Soviets an "illegal and self-styled authority." Mikołajczyk would serve in the Prime Minister's role until 24 November 1944, when, realizing the increasing powerlessness of the government in exile, he resigned and was succeeded by Tomasz Arciszewski, "whose obscurity", in the words of historian Mieczysław B. Biskupski, "signaled the arrival of the government in exile at total inconsequentiality." Stalin soon began a campaign for recognition by the Western Allies of a Soviet-backed Polish government led by Wanda Wasilewska, a dedicated communist with a seat in the Supreme Soviet, with General Zygmunt Berling, commander of the 1st Polish Army in Russia, as commander-in-chief of all Polish armed forces. By the time of the Potsdam conference in 1945, Poland has been relegated to the Soviet sphere of influence; an abandonment of the Polish government in exile that has led to the rise of the Western betrayal concept.