After the start of the Battle of Leyte, Volckmann's forces eliminated those Philippine Constabulary units created by the Japanese, who did not surrender. Volckmann organized the Commonwealth military and guerrilla resistance among the Ifugao's 11th Infantry Battalion: led by 1st Lieutenants: Francisco Balanban, Alpha Company; Guinid Tuguinay, Bravo Company; Pedro Dulnuan Sr., Administration. Volckmann's forces operated in the western and northern coasts of Luzon, launching attacks against the Japanese occupiers. During the U.S. and Filipino invasion of the Philippines in January 1945, Volckmann's guerrillas cut key communication lines and bridges and isolated barracks. Once the invasion had landed, he led attacks against the retreating Japanese forces far behind the lines, capturing bases and air fields, thereby allowing the American advance to proceed at a much quicker pace.