[1] Major General Gardner graduated from Memphis State University in 1960 with a Bachelor of Science degree in history and was a member of the Kappa Alpha Order.

From 1996 to 1999, he served as president and chief executive officer of the Intrepid Sea-Air-Space Museum in New York City.

On May 21, 2004, he was selected to fulfill the duties of president, Marine Corps University, becoming the first civilian to hold the post[2] He retired from that position on June 25, 2009.

The guest speaker at his retirement was GEN James T. Conway, Commandant of the Marine Corps, who referred to him as "the last Confederate general still on active duty" due to his research on America's Civil War.

Prior to assuming duties as president, MCU, Major General Gardner had served on the Commonwealth of Virginia's Veterans Services Foundation.