William Gainey enlisted in the Army in 1974. He served in Operation JOINT ENDEAVOR , Operation JOINT GUARD, and Operation JOINT FORGE in Bosnia and Herzegovina. He served as the Command Sergeant Major for the Combined Joint Task Force 7 and as the Command Sergeant Major of the Multi-National Corps Iraq in Operation IRAQI FREEDOM II. In 2005 he became the FIRST Senior Enlisted Advisor to the Chairman of the Joint Chiefs of Staff until his retirement in 2008.