Villamor was one of seven children. He studied commerce at De La Salle College (now DLSU-Manila) in Manila, hoping to pursue a business career. He joined the Philippine Army Air Corps (PAAC) Flying School in 1936 and was sent to the United States for training, and after three years, began flying B-17’s as part of the US Air Force’s Strategic Bombing Squadron. Upon his return to the Philippines, Villamor was assigned to lead the 6th Pursuit Squadron (now 6th Tactical Fighter Squadron) shortly before the Japanese invasion of the Philippines in December 1941. He was credited with destroying one enemy airplane in aerial combat early in the war. When his overwhelmed unit was finally destroyed, Villamor continued his war against the Japanese as an intelligence officer. On December 27, 1942 Villamor slipped past the Japanese Navy aboard the submarine “Gudgeon.” Establishing a chain of direct communication from the Philippines with General Douglas MacArthur in Australia, he coordinated the activities of various guerilla movements in Luzon, Mindanao and the Visayas.