The 11th fought a delaying retreat from
Lingayen Gulf to Bataan. At the fall of
Bataan in 1942, Volckmann refused to surrender and, accompanied by
Donald Blackburn, began a trek to northern
Luzon before the fall of
Corregidor. Sometimes in the company of other fleeing American and Filipino soldiers, Volckmann and Blackburn headed to the
cordillera in Northern Luzon. Once there, they hoped to assist in establishing an organized resistance against the Japanese. Volckmann strongly credits the assistance of Filipino civilians in making their journey a success, especially during their periods of illness, and time recovering at the American Fassoth Camp. On 20 August 1942, they reached Colonel
Thorp's camp west of
Fort Stotsenburg in the
Zambales Mountains. Thorp had been sent out from Bataan in January to organize guerrillas. On 24 August, they were guided to
Hukbalahap headquarters on
Mount Arayat, which then had them guided north to
La Paz, Tarlac. They made their way north to
Robert Lapham's camp, who then guided them further north to
Charlie Cushing's camp, where
Herb Swick joined them. On 9 September, they met Colonels
Noble and Moses, Captain Parker Calvert, and Lieutenant Arthur P. Murphy in North Luzon. Colonel Moses assumed command of guerrilla forces in North Luzon on 1 October 1942, and ordered coordinated attacks on Japanese forces starting on 15 October. Volckmann and Blackburn joined Lieutenant Rufino Baldwin, Philippine Army, in attacks on the Japanese garrisons in the Sanhiglo and
Balatoc area. Volckmann then established a new camp in
Kiangan, Ifugao on 8 December 1942. After being notified on 9 June 1943 of the capture of Colonels Moses and Noble, Volckmann took command of the two thousand man strong
USAFIP-NL. His orders from
Douglas MacArthur's
SWPA, were to "...limit hostilities and contact with the enemy to the minimum...your present mission as intelligence units can be of utmost value". On 24 November 1943, Volckmann organized his army into seven districts: 1st District under Major Parker Calvert, 2nd and 3rd Districts under Major George Barnett, 4th District under Major Ralph Praeger, 5th District under Major Romulo Manriquez, 6th District under Major
Robert Lapham, and the 7th District under Volckmann and Blackburn. Volckmann's claim to command some of these units is questionable. For example, Robert Lapham rejected Volckmann's efforts to command his guerrilla group. In early 1944, Volckmann established USAFIP-NL headquarters in western Benguet, and in August 1944, received a radio set allowing direct contact with SWPA for the first time since March 1943. On 30 October 1944, Volckmann's forces rescued
Mrs. Osmena and family from
Baguio. In November, Volckmann's forces were first supplied by submarine, the
USS Gar. After the start of the
Battle of Leyte, Volckmann's forces eliminated those
Second Philippine Republic Bureau of 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; they were 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, bridges, and isolated enemy
barracks. Once the invasion forces 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. Volckmann's guerrillas numbered about 8,000 men at the start of the
Battle of Luzon, but grew to 18,000 when supplied by the
Sixth United States Army. They consisted of five infantry regiments: the 11th, 14th, 15th, 66th, and the 121st, with Volckmann as the Commander, United States Armed Forces in the Philippines—Northern Luzon or USAFIP-NL (Military and Guerrillas). His force played an instrumental role in the
Battle of Bacsil Ridge,
Battle of Bessang Pass, and
Battle of Mayoyao Ridge. ==Post-World War II==