Koba settled in his hometown, but left it and hid in a village near Przeworsk, using the new name "Marcin Gruda". He became a member of the Service for Poland's Victory (later Home Army), helping with training, also organizing different acts of sabotage and training young soldiers of the Polish resistance. In the summer of 1944, he took part in Operation Tempest and for his services, he was twice awarded the Cross of Valor (in 1939 and 1944) as well as Cross of the Home Army.