[1] Born in East Orange, New Jersey, Castles graduated from the Valley Forge Military Academy in 1943.

He enlisted in the U.S. Army in May 1943 and was commissioned in 1944 after completing Infantry Officer Candidate School.

[2] After being discharged from active duty on April 15, 1946, Castles enrolled at the University of Virginia and earned a B.S.

He later completed courses at the United States Army Command and General Staff College in 1960 and 1964.

[2] Castles was confirmed as a United States Army Reserve brigadier general on February 8, 1974[3] and served as commander of the 116th Infantry Brigade (Separate) from 1977 to 1979.