Mr. Barnum was sworn in as the Deputy Assistant Secretary of the Navy for Reserve Affairs on 23 July, 2001, and was designated Acting Assistant Secretary of the Navy (Manpower and Reserve Affairs) on 20 January 2009 and retired on 30 April 2009.

Mr. Barnum was commissioned a second lieutenant in the U. S. Marine Corps in 1962. The fourth Marine to be awarded the nation’s highest honor, the Medal of Honor for valor in Vietnam, he retired from the Marine Corps in August 1989.
As a Marine Officer for over 27 and one-half years, Mr. Barnum served multiple tours as an artilleryman with both the 3rd and 2nd Marine Divisions to include two tours in Vietnam; 2nd Marine Aircraft Wing; Guard Officer at Marine Barracks, Pearl Harbor and Operations Officer, Hawaiian Armed Forces Police; Weapons Instructor at the Officer Basic School; four years at Marine Corps Recruit Depot, Parris Island as Commanding Officer, Headquarters Company and the 2nd Recruit Training Battalion of the Training Regiment; Chief of Current Operations, US Central Command where he planned and executed the first U.S./Jordanian joint exercise staff as the Commander of U.S. Forces and twice planned and executed  operation BRIGHT STAR spread over four southwest Asian countries involving 26,000 personnel .  Headquarters Marine Corps tours included: aide to the Assistant Commandant as a Captain and Deputy Director Public Affairs, Director Special Projects Directorate and Military Secretary to the Commandant as a Colonel. Upon retirement in 1989, Colonel Barnum served as the Principal Director, Drug Enforcement Policy, Office of the Secretary of Defense.

Mr. Barnum now serves on a number of corporate and non-profit boards including Segs4Vets and the Marine Corps Law Enforcement Foundation.   Mr. Barnum is married to Martha E. Hill of Parkersburg, West Virginia. The Barnums reside in Reston, Virginia.