page_title: 11th Armored Cavalry Regiment
section_title: Vietnam 1966–72
hierarchical_section_title: 11th Armored Cavalry Regiment / Vietnam 1966–72
caption_attribution_description: English: Engineers clear trail of mines in Cambodia.
context_page_description: The 11th Armored Cavalry Regiment is a unit of the United States Army garrisoned at Fort Irwin, California. Although termed an armored cavalry regiment, it is 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. The 11th ACR serves as the Opposing Force for the Army and Marine 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 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 2004, the 11th ACR deployed to Iraq. The 11th ACR was not reorganized under the U.S.
context_section_description: Home now for the regiment was Fort Meade, Maryland where the "Blackhorse" engaged in operational training and support activities like participation in the Presidential Inauguration and support for ROTC summer training.
  With the war in Vietnam escalating, the Blackhorse Regiment was alerted for assignment to Southeast Asia on 11 March 1966.  The regiment began specialized training for combat in a counterinsurgency environment.  Modifications were made to the organization and equipment (MTOE) with emphasis on the use of modified M113 armored personnel carriers (APCs).  Two M-60 machineguns with protective gun shield were mounted at the port and starboard rear of the vehicle, and a combination circular & flat frontal gun shield(s) were added around the .50 caliber machine gun located at the commander's hatch.  This combination produced a M-113 Armored Cavalry Assault Vehicle, or, in Vietnam more simply referred to as an ACAV by GIs, a name coined by 11th Armored Cavalrymen.
  The regiment's modifications emphasized the use of ACAVs instead of the Patton medium tank and completely replaced the M-114 found in reconnaissance platoons, which may have existed in European and CONUS areas of operation.  The M114 had been deployed to Vietnam in 1962, but withdrawn in 1964 due to its unsatisfactory, and often disastrous performance. Throughout the war, the tank companies, with their M48 Patton tanks, remained the same in each squadron.  In 1968, Colonel George S. Patton IV (son of World War II General Patton), commander of the 11th ACR in South Vietnam recommended to General Creighton Abrams that one squadron from a division and the other from theater command be issued the army's new aluminum tanks (Sheridans) for combat testing.  General Abrams concurred, and in January 1969, M551 Sheridans were issued to the 3rd Squadron 4th Armored Cavalry and the 1st Squadron 11th Armored Cavalry.  Due to differences between the organization of regimental cavalry squadrons and divisional cavalry squadrons, in 1st Sqdn 11th ACR, the Sheridans were issued to the ACAV troops, replacing three M113 ACAVs in each platoon (the squadron's one tank company remained intact); in 3rd Squadron, 4th Cavalry, the Sheridans replaced M48A3 tanks throughout.
  Although the 3/4 Cavalry met near disaster with their Sheridans within a month of receiving them (one destroyed by a mine), the 1/11 Cavalry had just the reverse in luck, killing nearly 80 enemy soldiers during an engagement on 23 February 1969.  All things considered, the army was satisfied with the Sheridan tank, and by the end of 1970 alone, well over 200 M551s would be in South Vietnam.  While nearly all US armored cavalry squadrons were equipped with the M551 by 1970, the 11th ACR tank companies, as well as the three US Army armor battalions (1/69th, 2/34th, and 1/77th Armor) in country, all retained their 90mm gun M48A3 Patton tanks.  Only the M48s, as well as the Australian Centurions, and ARVN M41 Walker Bulldog light tanks could effectively and safely conduct "thunder runs"; the firing of all tank weapons while driving down the highway or road. While ACAVs did not have a cannon, the Sheridan's high recoil from its 152mm main gun negated it from firing excessive broadsides while moving down a road.  Thus the most favored tanks for clearing highways with "thunder runs" on a daily basis, most often fell to the M48s of the 11th ACR and accompanying armor units.
caption: Engineers supported by a M551 Sheridan Tank from the Blackhorse Regiment clear mines in Cambodia.
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