He served in the leadership of the Communist Party of Poland's (KPP) youth organization in 1935-1936; disciplined by the Soviet leadership in 1936, a fact that later counted in his favour after Stalinist authorities had purged KPP. Mołojec put himself in charge of the Polish Workers' Party after the 1941 German invasion of the Soviet Union. He was assassinated by his own peers.[1]
In 1939 the Comintern put him in charge of the provisional leadership centre in Paris responsible for re-grouping the purged Polish communist movement. However, little was achieved in the atmosphere of suspicion surrounding the decimated KPP. In 1940 Mołojec was ordered to Moscow and attempts to re-form the KPP were abandoned by the Soviets.
In November 1942, when Nowotko was killed in mysterious circumstances, Mołojec put himself in charge of the PPR. Some weeks later, Mołojec was executed on the orders of Finder, Fornalska, Władysław Gomułka and Franciszek Jóźwiak, held responsible for arranging Nowotko's murder, a charge that has never been entirely convincingly proven (see also Marceli Nowotko).
In the Polish People's Republic, Mołojec was for many years a nonperson whose role in the Spanish Civil War and the formation of the PPR and its military wing were concealed or glossed over.