The 9th Engineer Battalion was constituted 15 May 1917 in the Regular Army as the 2nd Battalion Mounted Engineers. They were organized 21 May 1917 at Camp Newton D. Baker, El Paso, Texas, and redesignated the 9th Engineers (Mounted) in July 1917. The 9th spent its first years in El Paso while serving at Camp Stewart, Texas.
After World War I, the battalion was declared inactive except for A Company, which was transferred to Fort Riley, Kansas to provide engineer support to the Cavalry School. From 1923 to 1936, A Company provided vital training and infrastructure support to the Cavalry School first as a unit of the 2nd Cavalry Division and later as Troop A, 9th Engineer Squadron. The performance of Troop A during this period established a tradition of excellence for the 9th Engineer Squadron as a mounted cavalry unit. The platoon leader during a significant portion of that period was 1LT Samuel D. Sturgis, Jr., later to become the Chief of Engineers as a Lieutenant General.
Following the outbreak of World War I, the battalion was activated as the 9th Armored Engineer Battalion, part of the newly 9th Armored Division. Landing in France in September from their staging base in England, the 9th Armored Engineers supported the division's movement across France, making first contact with the enemy in the Schoenfels-Wilwerdange-Bissen area. The battalion fought in the Battle of the Bulge in December 1944, with C Company figuring prominently in the holding of Bastogne, for which the company was awarded the Distinguished Unit Citation.
On 7 March 1945, during the allied offensive to the Rhine River, Combat Command B of the 9th Armored Division arrived at the town of Remagen, discovering that the Ludendorff Bridge over the Rhine river was intact. A detachment from B Company braved enemy fire to cut wires and dismantle explosive charges set to destroy the bridge. Although several charges were detonated, the Wehrmacht failed to destroy the Ludendorff Bridge; B Company secured the far side of the bridgehead. The next day, C Company kept the bridge open despite a continuous, intense artillery and aircraft attack that struck the bridge twenty-four times. When the smoke cleared, the 9th Armored Engineers had been instrumental in establishing the first bridgehead across the Rhine River since the Napoleonic Campaigns. The unit was awarded the oak leaf for their Distinguished Unit Citation for the combat at Remagen.
The 9th Engineers were in the final sweep into Germany, and after the Nazi surrender, established an occupation headquarters in the Bavarian city of Bayreuth, with A Company at Coburg, B Company at Kulmbach, and C Company at Hof. Occupation duty ended in late 1945, so the battalion left West Germany and was deactivated on 13 October 1945.
In 1952, the 9th Engineers were reactivated as the 9th Engineer Combat Battalion (Army). In autumn of 1956, the 9th Engineer Battalion replaced the 35th Engineers at Kitzingen, Germany, moving to Aschaffenburg within the year.
In 1991, the 9th Engineer (Combat) Battalion served in the Persian Gulf War, leading the 1st Infantry Division through the Desert Breach, and assisted in liberating Kuwait. The battalion returned to Aschaffenburg, where it was deactivated in late 1991. The battalion was reactivated as part of the 1st Infantry Division in Schweinfurt, Germany on 5 April 1996; in October, it deployed with the 2nd Brigade Combat Team as part of the covering force for Operation Joint Endeavor and Joint Guard; the battalion returned to Schweinfurt in April 1997. The battalion deployed to Kosovo in June 1999 as part of Task Force Falcon. The battalion returned to Schweinfurt in December 1999, only to return for a second tour in Kosovo from May to November 2002.
In 2003, the 9th Engineers prepared to participate in the initial invasion of Iraq, by deploying select personnel with a large fleet of vehicles to Turkey, but that was cancelled because of Turkish refusal to participate in the Iraqi invasion. In August and September of that year, A Company deployed to Bosnia in support of Task Force 1-18’s Dynamic Response Exercise. In February 2004, the battalion deployed to Kuwait for month-long training before their last deployment, Operation Iraqi Freedom II.
The 9th Engineer Battalion, reorganized and augmented as Task Force 9th Engineer. The headquarters occupied Forward Operating Base Remagen in Tikrit, Salah ad Din province, but elements of it operated as far south as Balad and north into Bayji. In February 2005, the battalion redeployed to Schweinfurt, Germany. In March 2006, the 9th Engineer Battalion was permanently assigned to the 2nd Brigade Combat Team, 1st Infantry Division. On 28th March 2008, when the 1st Infantry Division completed its move to Fort Riley in Kansas the 9th Engineer Battalion came under operational control of 1st Armored Division.
In September 2006, the 9th Engineer Battalion was deployed for a second time in support of Operation Iraqi Freedom. Charlie Company was assigned to Ramadi, while the remainder were assigned to Baghdad. The 9th Engineer Battalion participated in the surge of OIF 06-08, and is slated to return to Schweinfurt, Germany, in mid November 2007.