The 278th Armored Cavalry Regiment (278th ACR, "Third Tennessee"), previously the 117th Infantry Regiment, is an armored brigade combat team of the Tennessee Army National Guard with headquarters in Knoxville, Tennessee. It is the only National Guard Armored Cavalry Regiment and one of only two in the entire US Army order of battle, the other being the active duty 11th ACR. The unit traces its lineage from the volunteer militias of Eastern Tennessee and has participated in conflicts from the Revolutionary War to the Global War on Terror. Missions State mission Provide trained and disciplined troops for domestic emergencies or as otherwise required by state law. Federal mission Maintain properly trained and equipped units available for prompt mobilization for war, national emergency, or as otherwise needed. Garrison units Headquarters 278th ACR (Saber) Headquarters and Headquarters Troop (HHT) 278th Armored Cavalry Regiment (278th ACR), Knoxville ("Warrior") Regimental Engineer Squadron (Phoenix) Headquarters and Headquarters Troop/Regimental Engineer Squadron, Lebanon ("Hawk") A/Regimental Engineer Squadron/278th Armored Cavalry Regiment, Dunlap (ENG) ("Apocalypse") Detachment 1 A/Regimental Engineer Squadron, Monteagle (ENG) ("Apocalypse") B/Regimental Engineer Squadron, Russellville (ENG) ("Berserker") C/Regimental Engineer Squadron, Knoxville (Signal)("Shockwave") D/Regimental Engineer Squadron, Nashville (MI) ("Darkhorse") Troop E Regimental Engineer Squadron, Smyrna ("Eagle") 1st Squadron (Cobra) Headquarters and Headquarters Troop/1st Squadron, Henderson ("Headhunters") Detachment 1, Headquarters and Headquarters Troop 1st Squadron, Selmer Troop A(-), Huntingdon ("Avenger") Troop B(-), Clarksville ("Brut") Detachment 1, Troop B, Springfield Troop C, Milan ("Carnage") Troop D, Ashland City Troop G, Humboldt ("Gladiator") Detachment 1 Troop G, Parsons 2nd Squadron (Phantom Raiders) Headquarters and Headquarters Troop(-), Cookeville ("Havoc") Detachment 1, Headquarters and Headquarters Troop, Gallatin Troop E(-), Jamestown ("Enforcer") Detachment 1 Troop E, Livingston Troop F, McMinnville ("Fox") Troop G, Crossville ("Gunslinger") Troop H, Rockwood Troop I, Lafayette ("Iron Fist") Detachment 1 Troop I(-), Gordonsville 3rd Squadron (Frontier) Note: This squadron was part of the Pennsylvania National Guard's 55th MEB. In 2021, it transferred to the Texas National Guard. Headquarters and Headquarters Troop, Temple, Texas ("Hydra") Troop H, Temple, Texas ("Heathen") Troop I, Gatesville, Texas ("Imperial") Troop K, Temple, Texas ("Krusher") Troop L, Temple, Texas ("Legion") 4th Squadron (Peacemaker) Headquarters and Headquarters Troop, Mount Carmel ("Highlander") Troop D (-), Clinton ("Dakota") Detachment 1, Troop D, Rogersville Troop N, Sweetwater ("Nightmare") Troop O, Newport ("Outrider") Troop P, Greeneville, ("Pathfinder") Troop Q, Rockwood, ("Quickdraw") Support Squadron (Thunderbolt) Headquarters and Headquarters Troop, Columbia ("Atlas") Troop A(-) (Supply & Transportation), Lobelville ("Stallions") Detachment 1, Troop