The Soviets quickly Sovietized the annexed lands , introducing compulsory collectivization . They proceeded to confiscate , nationalize and redistribute private and state @-@ owned Polish property . In the process , they banned political parties and public associations and imprisoned or executed their leaders as " enemies of the people " . In line with Soviet anti @-@ religious policy , churches and religious organizations was persecuted . On 10 February 1940 , the NKVD unleashed a campaign of terror against " anti @-@ Soviet " elements in occupied Poland . The Soviets ' targets included persons who often traveled abroad , persons involved in overseas correspondence , Esperantists , philatelists , Red Cross workers , refugees , smugglers , priests and members of religious congregations , the nobility , landowners , wealthy merchants , bankers , industrialists , and hotel and restaurant owners . Stalin , like Hitler , worked to eliminate Polish society .