Events taking place in 1943 significantly weakened the Polish government in exile . A rift developed between Poland and the Soviet Union , an increasingly important ally for the West , particularly after the revelation of the Katyn massacre in 1943 ( on 13 April ) , followed by the breaking-off of diplomatic relations with Poland by the Soviets ( on 21 April ) . The subsequent death ( on 4 July ) of the charismatic General Sikorski , succeeded by less influential Stanisław Mikołajczyk as the Prime Minister , and General Sosnkowski as the Commander-in-Chief , contributed to the decline . No representative of the Polish government was invited to the Tehran Conference ( 28 November 28 – 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 , assigning it to the Soviet sphere of influence . 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 the PKWN was proclaimed in 1944 . PKWN 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 . " The communists refused to deal with the Underground State just like they refused to deal with the government in exile ; its leaders and soldiers in " liberated " Polish territories were persecuted . A number of prominent leaders of the Underground State , including the Government Delegate , Jan Stanisław Jankowski and the last AK Commander-in-Chief , General Leopold Okulicki , who decided to reveal themselves and upon the Soviet invitation begun open negotiations with the communist authorities , were arrested and sentenced by the Soviets in Moscow in the infamous Trial of the Sixteen ( arrests were carried out in March 1945 , and the trial itself took place in June that year ) . On 27 June 1945 the Council of National Unity held its last session , issuing a 12-point declaration demanding that the Soviet army leave Poland and the repression of the non-communist political parties cease . The Government Delegate 's Office at Home , restructured after the arrests of its leadership and headed by the last Delegate , Stefan Korboński , disbanded on 1 July , after the creation in Moscow of the Provisional Government of National Unity ( Tymczasowy Rząd Jedności Narodowej , TRJN ) on 28 June 1945 . The disbanding of those structures marked the end of the Underground State
Yalta Conference
Yalta Conference
Polish Underground State