Complex sentence: Communist politicians cooperated with the left-wing PPS faction led by Józef Cyrankiewicz, prime minister under new president Bierut from February 1947, who personally visited Stalin in Moscow in March 1948 with the idea of a party merger.
Split into simpler sentences: Communist politicians cooperated with the left-wing PPS faction led by Józef Cyrankiewicz, prime minister under new president Bierut from February 1947. Cyrankiewicz visited Stalin in Moscow in March 1948 to discuss the idea of a party merger.