After World War II, he strongly criticized communist order in Poland. It brought him immense popularity among believers. Between 1945 and 1947, he worked as hospital chaplain in Gorlice and from 1947 to 1948 in Krynica. It was there that he entered an armed unit of anti-communist underground Polish opposition; specifically, the Polish Underground Independency Army (Polska Podziemna Armia Niepodległościowa, PPAN). He was awarded the rank of captain. While serving with the army he convinced partisans to not carry out executions of Soviet NKVD collaborators and members of Polish Workers' Party and activists, who were beaten and forced to eat communist party identity cards.