General Grizzle’s military career began in 1971. He was commissioned as an infantry officer upon completion of Federal Officer Candidate School in 1972. Prior to this assignment, General Grizzle served as Commander of the 90th Troop Command (Oklahoma Army National Guard); Commander of the 45th Infantry Brigade (Oklahoma Army National Guard); and Deputy State Area Commander of the Oklahoma National Guard. While Deputy Commander of the 45th Infantry Brigade, he participated in the security effort following the April 1995 bombing of the Alfred P. Murrah Federal Building in Oklahoma City. Most recently, he served as Vice Director for Joint Training at U.S. Joint Forces Command in Norfolk, Va., while additionally serving as Vice Commander of the Joint Warfighting Center in Suffolk, Va.
Immediately after the attacks of September 11, 2001, Major General Grizzle entered active federal service and took command of the Department of Defense Joint Task Force -Civil Support (JTF-CS), the only unit in the Department of Defense responsible for the planning and execution for the response to any possible Weapons of Mass Destruction attack within the United States.