founded to organize these and other parties. History Establishment and Sovietization period The Polish United Workers' Party was established at the unification congress of the Polish Workers' Party and Polish Socialist Party during meetings held at the main building of Politechnika Warszawska (Warsaw University of Technology) from 15 to 21 December 1948. The unification was possible because the PPS activists who opposed unification (or rather absorption into the Workers' Party) had been forced out of the party. Similarly, the members of the PPR who were accused of "rightist–nationalist deviation" () were expelled. Thus, the PZPR was a renamed and enlarged PPR for all intents and purposes. "Rightist-nationalist deviation" was a political propaganda term used by the Polish Stalinists against prominent activists, such as Władysław Gomułka and Marian Spychalski who opposed Soviet involvement in the Polish internal affairs, as well as internationalism displayed by the creation of the Cominform and the subsequent merger that created the PZPR. It is believed that it was Joseph Stalin who put pressure on Bolesław Bierut and Jakub Berman to remove Gomułka and Spychalski as well as their followers from power in 1948. It is estimated that over 25% of socialists were removed from power or expelled from political life. Bolesław Bierut, an NKVD agent and a hardline Stalinist, served as first Secretary General of the ruling PZPR from 1948 to 1956, playing a leading role in imposing communism and the installation of its repressive regime. He had served as President since 1944 (though on a provisional basis until 1947). After a new constitution abolished the presidency, Bierut took over as Prime Minister, a post he held until 1954. He remained party leader until his death in 1956. Bierut oversaw the trials of many Polish wartime military leaders, such as General Stanisław Tatar and Brig. General Emil August Fieldorf, as well as 40 members of the Wolność i Niezawisłość (Freedom and Independence) organisation, various Church officials and many other opponents of the new regime including Witold Pilecki, condemned to death during secret trials. Bierut signed many of those death sentences. Bierut's mysterious death in Moscow in 1956 (shortly after attending the 20th Congress of the Communist Party of the Soviet Union) gave rise to much speculation about poisoning or a suicide, and symbolically marked the end of Stalinism era in Poland. Gomułka's autarchic communism In 1956, shortly after the 20th Congress of the Communist Party of