Lieutenant General H. R. McMaster is a research fellow at the Hoover Institution. He was a national security affairs fellow at Hoover from 2002 to 2003.

He assumed duties as the Director, Army Capabilities Integration Center and Deputy Commanding General, Futures, US Army Training and Doctrine Command on 15 July 2014. Prior to his arrival at Fort Eustis he served as Commanding General, Maneuver Center of Excellence and Fort Benning from June 2012 to July 2014. Previously he served as Commander, Combined Joint Inter-Agency Task Force Shafafiyat (Transparency) in Kabul, Afghanistan. He was commissioned as an officer in the United States Army upon graduation from the United States Military Academy in 1984. He holds a PhD in military history from the University of North Carolina at Chapel Hill.

LTG McMaster's previous command assignments include Eagle Troop, Second Armored Cavalry Regiment in Bamberg, Germany and in Southwest Asia during the 1991 Persian Gulf War; 1st Squadron, 4th Cavalry in Schweinfurt Germany from 1999 to 2002; and 3d Armored Cavalry Regiment at Fort Carson, Colorado and in Iraq from June 2004 to June 2006. Staff assignments include Director of Concept Development and Learning at the U.S. Army Training and Doctrine Command from August 2008 to May 2010; Special Assistant to the Commander, Multinational Force-Iraq from February 2007 to May 2008; Director, Commander's Advisory Group at US Central Command from May 2003 to 2004; and squadron executive officer and regimental operations officer in the 11th Armored Cavalry Regiment from July 1997 to July 1999. He also served as an assistant professor of history at the United States Military Academy from 1994 to 1996.

He is the author of the award-winning book Dereliction of Duty: Lyndon Johnson, Robert McNamara, the Joint Chiefs of Staff, and the Lies That Led to Vietnam. He has published numerous articles on historical and national security affairs topics in edited volumes, newspapers, magazines, and professional journals.  He is a member of the Council on Foreign Relations, contributing editor for Survival magazine and a senior consulting fellow at the International Institute for Strategic Studies in London.