Gayle graduated from Sunset High School, Dallas Texas in 1934. Gayle briefly enrolled at Southern Methodist University in Dallas, Texas, before transferring to the U.S. Naval Academy in Annapolis, Maryland. He graduated from the academy on June 1, 1939 and received a commission in the U.S. Marine Corps as a second lieutenant.
On American's entry into World War II, Gayle—promoted to captain in May 1942—sailed to Wellington, New Zealand, with the 1st Marine Division. From there he participated in the invasion of Guadalcanal. He subsequently served during the battles of New Britain and Peleliu.
Gayle received the Bronze Star for his actions on New Britain and the Navy Cross and Purple Heart for his actions and wounding on Peleliu.
He returned to the United States in November 1944. Promoted to lieutenant colonel, he taught at the Command and Staff School, Marine Corps Schools, Quantico, Virginia.
Gayle served in several posts over coming years, including Assistant Director of Marine Corps History. At that time he authored Bloody Beaches: The Marines at Peleliu.
As Executive Officer, 7th Marines, 1st Marine Division, Gayle saw combat during the Korean War. During that conflict he received the Navy Commendation Medal and the Legion of Merit with Combat "V" for exceptionally meritorious service.
After the war he again served in various posts, including—after a stint in the National War College—Deputy Assistant Chief of Staff, G-3, Headquarters, U.S. Forces, Japan.
Gayle retired from active duty on January 31, 1968, with the rank of brigadier general. He subsequently joined the Center for Strategic and International Studies at Georgetown University.
According to Gayle's official biography:
"A complete list of the general's medals and decorations includes: the Navy Cross, the Legion of Merit with Combat 'V' and Gold Star in lieu of a second award, the Bronze Star Medal with Combat 'V', the Navy Commendation Ribbon with Combat 'V', the Purple Heart, the Presidential Unit Citation with two stars indicative of second and third awards, the American Defense Service Medal, the American Campaign Medal, the Asiatic-Pacific Campaign Medal with one silver star in lieu of five bronze stars, the World War II Victory Medal, the National Defense Service Medal with one bronze star, the Korean Service Medal with two bronze stars, the United Nations Service Medal, and the Korean Presidential Unit Citation."