[2][4][3] Following demobilization, Kubilius set to work in the Kaunas radio broadcast service and later the Vilnius tobacco factory.

In 1943 he joined the Lithuanian Liberty Army (LLA), heading its organizational communications department in the headquarters in Vilnius under the rank of captain.

[2][4][3] Upon return, Kubilius began establishing bunkers as well as initiating communications with the LLA's Šiauliai district, as well as other partisan groups in Samogitia.

Along with fellow partisan Adolfas Eidimtas he established the Samogitian Legion, a progenitor of the Žemaičiai military district.

[6][7] He took care of the acquisition of weapons, collected information about the Red Army, the as well as deployment of its military units, and the movement of equipment.