1st Battalion, 18th Infantry Regiment
"Vanguards"

The 1st Battalion, 18th Infantry, a mechanized infantry battalion assigned to the 1st Infantry Division's 2nd Brigade Combat Team, was first constituted on 3 May 1861 in the Regular Army as Company B, 2nd Battalion, 18th Infantry. It was organized on 17 September 1861 at Camp Thomas, Ohio.

The unit was redesignated on 20 September 1861 as Company H, 1st Battalion, 18th Infantry, on 19 October 1861 as Company A, 1st Battalion, 18th Infantry, and again reorganized and redesignated on 21 September 1866 as Company A, 18th Infantry.

The unit was consolidated in April 1869 with Company E, 25th Infantry. Company E, 25th Infantry was first constituted on 3 May 1861 in the Regular Army as Company E, 2d Battalion, 16th Infantry and organized on 2 May 1865 at Fort Ontario, New York. It as reorganized and redesignated on 21 September 1866 as Company E, 25th Infantry. The consolidated unit was designated as Company A, 18th Infantry. The 18th Infantry was assigned on 8 June 1917 to the 1st Expeditionary Division, which was later redesignated as the 1st Infantry Division.

The unit was reorganized and redesignated on 15 February 1957 as Headquarters and Headquarters Company, 1st Battle Group, 18th Infantry, and remained assigned to the 1st Infantry Division with its organic elements concurrently constituted and activated. It was relieved on 14 April 1959 from assignment to the 1st Infantry Division and assigned to the 8th Infantry Division.

It was relieved on 1 April 1963 from assignment to the 8th Infantry Division and assigned to the 1st Infantry Division. The unit was reorganized and redesignated on 2 January 1964 as the 1st Battalion, 18th Infantry. This unit was inactivated on 1 November 1983 at Fort Riley, Kansas, and relieved from assignment to the 1st Infantry Division.

It was assigned on 16 June 1989 to the 197th Infantry Brigade and activated at Fort Benning, Georgia, before being relieved on 16 August 1991 from assignment to the 197th Infantry Brigade and assigned to the 24th Infantry Division. It was relieved on 16 February 1996 from assignment to the 24th Infantry Division and assigned to the 1st Infantry Division.

The 1st Infantry Division was a mechanized infantry, or "Heavy" Division, and in the late 1990s was in the process of converting to the new Force XXI force structure. The new design made several important changes. At the battalion level, it decreased the number of companies, but increased the size of the remaining companies. This process was commonly known as LCD XXI. The 18th Infantry LCD XXI conversion began on 7 May 1999, when Company D was inactivated and cased it's Guidon. 1-18th Infantry subsequently consisted of HHC, A, B, and C Companies. This change added an additional 9-man squad to each platoon. Each platoon had 4 M2 Bradley Infantry Fighting Vehicles, one 9-man Weapons Squad, and 2 9 man Maneuver Squads.

A mechanized infantry battalion under the Force XXI structure was composed of a Headquarters and Headquarters Company and 3 line maneuver Companies (A, B, and C), utilizing 44 Bradley Fighting Vehicles and a number of HMMWVs and other vehicles. A line maneuver Company consisted of 5 Officers and 130 Enlisted Men, with 3 Platoons utilizing 14 Bradleys. Each Platoon has 4 Bradley crews and 3 9-man Infantry Squads (2 rifle squads and one heavy weapons squad). The HHC contained the command group and staff, the Scout Platoon, Mortar Platoon (with 120mm mortars), Medical Platoon, Sniper Section, and other support personnel. The 1st Battalion, 18th Infantry, was authorized 36 Officers, 1 Warrant Officer and 666 Enlisted, for a total of 703 soldiers. At the time of the conversion the 1st Battalion, 18th Infantry's home duty station was located with the 2nd Brigade at Conn Barracks near Schweinfurt, Germany.

1-18th Infantry deployed with other elements of the 2nd Brigade, 1st Infantry Division (Mechanized) deployed from Germany in support of Operation Iraqi Freedom in 2006. In July 2006, while the Brigade was deployed as part of OIF, the Headquarters of the 1st Infantry Division cased its colors in Germany, and returned to the United States, uncasing its colors in August 2006 at Fort Riley, Kansas. The 2nd Brigade Combat Team remained based in Germany until March 2008, when the Brigade (along with the 1-18th Infantry) return from its deployment to OIF.

In March 2008 the 2nd Brigade, 1st Infantry Division (Mechanized) in Germany was inactivated and reflagged as the 172nd Infantry Brigade (Seperate). The 2nd Brigade, was reorganized and reactivated as a modular Brigade Combat Team at Fort Riley in April 2008. Some elements previously assigned, including the 1-18th Infantry, were concurrently reorganized and reactivated.