 He was a co-founder, trustee, and president emeritus of the Marine Military Academy in Harlingen, Texas.Having joined the Virginia National Guard in 1931 and served on its rifle team, McIlhenny transferred to the U.S. Marine Corps Reserve in 1935, attended Platoon Leaders Class, and served as captain of the U.S. Marine Corps Reserve rifle team.Called to active duty when the United States became involved in World War II, McIlhenny spent 31 months in the western Pacific as a member of B Company, 1st Battalion, 5th Marines, 1st Marine Division.