In 1922 he was asked to join the
Philippine Constabulary and revitalize their medical services; he joined and had by 1926 been promoted to lieutenant colonel and chief surgeon, serving as medical inspector from 1926 to 1934. Valdes became brigadier general and chief of the Constabulary in 1934. He later took his oath of office as Deputy Chief of Staff of the Philippine Army on May 4, 1936, and with the retirement of
Chief of Staff General
Paulino Santos, Valdes assumed this office by presidential appointment on January 1, 1939. With the growing threat of Japanese expansion during the 1930s, President
Manuel L. Quezon established the
Department of National Defense in November 1939, which had executive authority over the army. With the
attack on Pearl Harbor and
Japanese invasion of the Philippines in December 1941, President Quezon merged the departments of National Defense, Public Works, Communications and Labor into a single department and appointed Valdes as secretary on December 23. Valdes received one of 20 original facsimiles of the Instrument of Surrender, being one of eight personal guests of MacArthur, and his document is currently owned and curated by
The International Museum of World War II in
Natick, Massachusetts. In January 1946 Valdes was appointed as one of the judges at the Military Tribunal of Japanese General
Masaharu Homma in view of the
war crimes committed by his command during the
invasion of the Philippines, sitting on the bench along with Leo Donovan, Robert G. Gard,
Arthur Trudeau, and Warren H. McNaught. ==Personal life==