The Army’s premier proponent of unconventional warfare, Special Forces traces its historical roots from the elite Army formations of World War II and the Office of Strategic Services, or OSS. The OSS was formed in World War II to gather strategic intelligence and conduct operations behind enemy lines in support of resistance groups in Europe and the Far East. After the war, individuals such as Colonel Aaron Bank, a former OSS operative, and Colonel Wendell Fertig and Lieutenant Colonel Russell Volckmann, both of whom fought as guerrillas in the Philippines, used their wartime experience to formulate the doctrine of unconventional warfare that became the cornerstone of SF. In the Army’s official lineage and honors, the SF groups are linked to the regiments of the First Special Service Force, an elite combined Canadian-American unit that fought in the Aleutians, Italy and southern France.