Battle of Luzon
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. This 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.