After being admitted to the Philippine Bar in 1914, he was appointed as a law clerk for the Philippine Commission. He quickly rose through the ranks and was promoted to the position of Chief Clerk of the Department of the Interior in 1917. In 1918 he served as the legislative secretary to SpeakerSergio Osmeña of the House of Representatives and in 1936 was appointed by President Manuel L. Quezon as his Executive Secretary, becoming the first in the country to serve in such a position. When the Japanese invaded the country in 1941, Vargas was designated to the Department of National Defense as its secretary. A few weeks later, he was appointed by President Manuel Quezon as mayor of the City of Greater Manila in 1941. His responsibilities included administering the open city upon the arrival of occupational troops of the Imperial Japanese Army on January 2, 1942. By 1942, Vargas became chairman of the Japanese-sponsored Philippine Executive Commission. During the collaborationist Second Philippine Republic, he was once asked by the Japanese to assume the Presidency, but he declined. He instead served as the regime's Ambassador to Japan. In that position, he was quoted shortly before Japanese troops were driven from Manila as stating that "we know Japan is destined for sure victory and prosperity for ages to come." Vargas served as Chairman of the National Planning Commission from 1946–1954 and was a member of the Board of Regents of the University of the Philippines from 1961-1965. In 1960, the Republic of the Philippines conferred on him the Legion of Honor with the rank of Commander.
Scouting
Vargas' involvement with Scouting started in 1935 when he became a member of the executive board of the Philippine Council of the Boy Scouts of America. Together with other Philippine Scouting advocates he became one of the charter members of the Boy Scouts of the Philippines in 1936. Upon the death of Manuel Camus in 1949, Vargas was unanimously chosen by the National Executive Board to serve as the BSP's President and Chief Scout of the Boy Scouts of the Philippines. He served the position of National President until 1961. He became a member of the World Scout Committee of the World Organization of the Scout Movement from 1951 to 1957. Vargas was awarded the Bronze Wolf in 1959 and received other awards including the Silver Tamaraw, Silver Fox, Silver Ibex, Silver Wolf, and in 1959 also received the highest distinction of the Scout Association of Japan, the Golden Pheasant Award. He also became the first recipient of the Tanglaw ng Kabataan Award of the BSP in 1961.
