The 11th Armored Cavalry Regiment ("Blackhorse Regiment") is a unit of the United States Army garrisoned at Fort Irwin, California. Although termed an armored cavalry regiment, it is currently being re-organized as a multi-component heavy brigade combat team. The regiment has served in the Philippine–American War, World War II, the Vietnam War, Cold War, Operation Desert Storm, and Operation Iraqi Freedom (Iraq War). The ACR was serving as the Opposing Force (OPFOR) for the Army, Marine, and National Guard task forces, and foreign military forces that train at the National Training Center.
The OPFOR trained U.S. Army forces in mechanized desert warfare following a Soviet-era style threat until June 2002, when the OPFOR and the 11th ACR changed to portraying an urban/asymmetrical warfare style of combat U.S. soldiers are currently facing in operations abroad. From June to December 2003, members of the 11th ACR deployed to Afghanistan, where they helped to develop and train the armor and mechanized infantry battalions of the Afghan National Army. These specialized units would defend the Afghan capital during the country's constitutional convention. In January 2005, the 11th ACR deployed to Iraq. The 11th ACR was not reorganized under the U.S. Army Combat Arms Regimental System, but has been reorganized under the U.S. Army Regimental System.