By the time Col. H.R. McMaster led elements of his 3rd Armored Cavalry Regiment (3rd ACR) into northern Iraq's Nineveh (Ninewa) Province in May of 2005, he had already established a reputation within the Army as a highly-respected and innovative officer. During the 1991 Gulf War, Captain McMaster had commanded Eagle Troop of the 2nd ACR and during the 1991 engagement known as the Battle of 73 Easting, his cavalry troop overran and destroyed a numerically superior Iraqi Republican Guard force, taking no casualties. For this action, he was awarded the Silver Star.
He later earned a Ph.D. in history from the University of North Carolina at Chapel Hill and taught history at the US Military Academy. He commanded 1st Squadron, 4th Cavalry Regiment from 1999 until 2002 and in the spring of 2003, McMaster joined the staff of General John Abizaid at Central Command. He assumed command of 3rd ACR in June of 2004, leading the unit from Fort Carson, Colorado to Iraq in January 2005 for its second deployment.