80 percent destroyed in the aftermath of the Warsaw Uprising of 1944. The Polish state acquired more highly developed western territories and lost the more economically backward eastern regions. Already in 1948 the prewar level of industrial production was exceeded in global and per capita terms during the Three-Year Plan (Plan Trzyletni), implemented first and fueled by the collective desire to rebuild shattered lives. The Three-Year Plan was the work of the Central Planning Office led by Czesław Bobrowski and PPR economist Hilary Minc, who declared the need to preserve elements of market capitalism. Standard of living of the population of Poland markedly improved. Soviet pressure caused the Polish government to reject the American-sponsored Marshall Plan in 1947 and to join the Soviet Union-dominated Comecon in 1949. Warsaw and other ruined cities were cleared of rubble — mainly by hand — and rebuilt with great speed (one of the successes of the Three-Year Plan) at the expense of former German cities like Wrocław, which often provided the needed construction material. Wrocław, Gdańsk, Szczecin and other formerly German cities were also completely rebuilt. Historian Norman Davies wrote that the new Polish frontiers, from the Polish interests point of view, entirely advantageous, but realized at the cost of enormous suffering and specious justifications. The radically new Eastern European borders constituted a "colossal feat of political engineering", but could not be derived from immemorial historical determinations, as claimed by the communist propaganda. Consolidation of communist power Already before the Red Army entered Poland, the Soviet Union was pursuing a strategy of eliminating pro-Western resistance as an organized force to ensure that Poland would fall under its sphere of influence. In 1943, following the revelation of the Katyn massacre, Stalin suspended relations with the Polish government-in-exile in London. At the February 1945 Yalta Conference, the Soviet Union agreed to allow the formation of a coalition government composed of the communists, including the Polish Workers' Party (Polska Partia Robotnicza, PPR), as well as Polish pro-Western elements in exile and in Poland, and subsequently to arrange for free elections to be held. After the prewar Communist Party of Poland was eliminated in Stalin's purges in 1938 (some five thousand Polish communists were brought to Russia and killed), a group of survivors led by Marceli Nowotko, Bolesław Mołojec and Paweł Finder convinced in 1941 the Soviets in Moscow of the need to reestablish a Polish party. The