The 1st Battalion, 12th Infantry Regiment was formerly assigned to the 3d Brigade Combat Team of the U.S. 4th Infantry Division at Fort Carson and deployed with the 3rd BCT in March 2003 in support of Operation Iraqi Freedom I. From May 2003 to February 2004, the battalion and elements of 1-68 Armor and 4th Engineers was attached to 173rd Airborne Infantry Brigade while B/1-12 remained with 1-68 Armor under 3rd Brigade/4th Infantry Division. The battalion redeployed back to Fort Carson in March 2004. As a result of the transformation of the brigade to the modular concept, elements of the battalion were changed to a cavalry squadron, the 2nd Squadron, 9th Cavalry Regiment in November 2004. 1st Battalion, 12th Infantry Regiment was reactivated at Fort Hood as part of the 4th BCT, 4th Infantry Division and deployed to Baghdad, Iraq, in fall of 2005 in support of Operation Iraqi Freedom. It was replaced in the fall of 2006 by the 2nd BCT, 2nd Infantry Division from Fort Carson. This unit was temporarily assigned to 1st Cavalry Division to which the 2d Battalion, 12th Infantry Regiment was attached until February 2007 when the 4th BCT, 1st Infantry Division was assigned tactical control of Baghdad. On 6 April 2015 the 1st and 2nd Battalions, 12th Infantry Regiment were re-flagged under the 2nd IBCT, 4th Infantry Division, Fort Carson, Colorado.
