In 1942, Kumor initiated and organized "Operation Góral", a successful heist during which a German money transport worth 105 million Polish zlotys was captured.

1 in Lviv;[8] in turn – until the outbreak of the war – he was an ordnance officer of Brigadier General Michał Karaszewicz-Tokarzewski, commander of the Corps District No.

During the September Campaign in 1939, Kumor took part in the Battle of the Bzura, and then, along with General Tokarzewski and a group of a dozen or so officers, he managed to get into besieged Warsaw.

As a member of General Tokarzewski's staff, he took an active part in forming the first underground resistance organization in the country: The Service for Poland's Victory.

During that time, he organized an insurgent grenade factory and contributed to the detection and protection of large grain stocks in Haberbusch's warehouses, later used to feed the fighters of Warsaw.

After his release, Kumor devoted himself to journalistic work, publishing a number of articles in magazines about the activities of the Polish resistance during the occupation.