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 Iraq War (2004-05 and 2009-10). In May 2025, the Pentagon announced that the 278th Armored Cavalry Regiment will convert to a Mobile Brigade Combat Team.
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.
History Formation of predecessor units The Third Brigade of the Tennessee Militia was absorbed into the National Guard of the United States on 25 March 1887 as the 3rd Infantry Regiment, with headquarters in Knoxville. The 1st Battalion was located in Knoxville, and the 2nd Battalion was located in Chattanooga. In the spring of 1898, the battalions were consolidated to form the 6th Infantry Regiment. Between 18 and 20 May 1898, the 6th Infantry was re-designated as the 3rd Tennessee Volunteer Infantry Regiment..
Spanish–American War The 3rd Tennessee was mustered into federal service from 18–20 May 1898 at Camp Dewy, Nashville, for the war with Spain. The 3rd Tennessee was deployed to Tampa, Florida, and later mustered out of federal service at Anniston, Alabama, on 31 January 1899. It was reorganized in Knoxville in the Tennessee National Guard as the 6th Infantry Regiment. In 1903, the 6th Infantry Regiment was redesignated once again as the 3rd Infantry Regiment.
Mexican Punitive Expedition On 3 July 1916, the 3rd Infantry Regiment was mustered into federal service at Nashville and deployed to Eagle Pass, Texas, to take part in the Army's pursuit of the Mexican bandit Francisco "Pancho" Villa along the Mexico-U.S. border. They returned home and were mustered out of federal service on 14 March 1917.
World War I Four months after returning from Texas, on 24 July 1917, the 3rd Infantry Regiment was mustered into federal service and assigned as an element of the 30th Division. On 3 August, the War Department ordered concentration and organization of the units designated to form the division at Camp Sevier, Greenville, South Carolina. On 5 August 1917 the 3rd Tennessee Infantry Regiment was "drafted" into federal service. Concentration continued throughout August 1917.
The 30th Division (the "Old Hickory" Division, named after President Andrew Jackson of Tennessee) was reorganized in accordance with the tables of organization of 8 August 1917. On 12 September 1917 infantry brigades were organized in the 30th Division. The 59th Infantry Brigade was composed of the 3rd Tennessee and the 1st South Carolina Regiments of Infantry, and detachments of the 1st North Carolina and 2nd South Carolina Regiments of Infantry, and the Tennessee Cavalry. The 60th Infantry Brigade included, the 2nd and 3rd North Carolina Regiments of Infantry, and detachments of the 1st North Carolina and 2nd Tennessee Regiments of Infantry and of North Carolina Cavalry. On 14 September 1917 the 3rd Tennessee Infantry Regiment was reorganized and re-designated as the 117th Infantry Regiment assigned to the 30th Division.
The 30th Division underwent systematic training from 17 September until 30 April 1918. During October 1917, Selective Service men from Camps Gordon, Jackson and Pike completed the regiment and filled out the rest of the division.
The 117th Infantry Regiment as part of the 59th Brigade, 30th Infantry Division received its first taste of war on 9 July 1918. With the 27th (US) Division, it was assigned to the organization and defense of the East Poperinghe Line, a third defensive position in the Dickebusch Lake and Scherpenberg Sectors. The 30th Division on 11 July 1918 assumed full responsibility for the East Poperinghe trench system.
Affiliated with the British, 117th Infantry Regiment as part of the 30th Division reached the front lines for training on 16 July 1918 and remained until 18 August. Actual training was carried until 9 August. The 117th Infantry Regiment and the rest of the 59th Infantry Brigade remained with the British 3rd (GB) Division, while the machine gun and infantry units served by battalions and other divisional troops by detachments remained with 30th Division.
After a brief return to the rear for further training, the 30th Division relieved the 3rd (GB) Division in the front line of the Canal Sector from the vicinity of Elzenwalle to the railroad southeast of Transport Fme on the nights of 16 and 17 August 1918. On 18 August 1918 the 30th Division (US) assumed command, with the 6th (GB) Division to its right. On the next day the Canal Sector occupation was merged into the Ypres-Lys Operation.
From 19 August until 4 September 30 (US) Division, less Artillery and 105th Ammunition Trains took part in the Ypres- Lys Operation. 26 August – 11 September rumors of a German withdrawal of troops was investigated. 31 August combat patrols of the 30th (US) Division determined that the Germans were withdrawing. The next day, the 59th Infantry Brigade leading, the division captured Moated Orange, Voormezeele, Lock No. 8, and Lankhof Fme, and occupied a line connecting these localities with the original front at Gunners' Lodge. The 27th (US) Division served to the right, the 14th (GB) Division to the left.
On the nights of 3 through 5 September, the 30th Division (US) was relieved by the 35th (GB) Division, and on 4 September, the command passed. The 30th (US) Division concentrated near Proven on 5 September and 6, and moved into the St. Pol Area, in the zone of the British First Army on 7 September for training.
Meanwhile, on 12–15 September, the 37th Infantry Division, along with the two 30th Division units, occupied the Avocourt Sector on 23–25 September 1918.
The 30th (US) Division, less artillery, and the 105th Ammunition Train participated in the Somme Offensive Operation 22 September – 1 October. On the nights of 21 to 24 September 1918, the 30th (US) Division moved to the Tincourt-Boucly (British Fourth Army) Area, where the Second Corps was affiliated with the Australian 1st Division, east of Villeret and Hargicourt. The lines extended from 300 meters east of Buisson-Gaulaine Fme, through La Haute Bruyere, la Terrasse Trench, Bois des Tuyas, Boyeu du Chevreau, to Malakoff Fme. The 59th Infantry Brigade occupied the forward area. Command passed to the 30th (US) Division on 24 September 1918.
On 26–27 September 30 (US) Division attacked from a line of departure between 300 and 400 meters east of the line between La Haute Bruyere and Malakoff Fme, with the 46th (GB) Division on the right, and the 27th (US) Division on the left. On the night of 27 September and 28, the 60th Infantry Brigade relieved the 59th Infantry Brigade and the 117th Infantry Regiment.
On 29 September 1918 the 30th (US) Division with the 59th and 60th Infantry Brigades in the lead, battered through the formidable Hindenburg Line. Immediately after the penetration, the 30th Division crossed the canal and captured Bellicourt, then entered Nauroy. It was at Bellicourt, France, that the 30th Division smashed its way through the "Hindenburg Line", a victory that hastened the close of the war.
The 5th Division (Australia) moved up to pass through the 30th (US) Division, and both divisions advanced to establish a front from the intersection of Wattling Street road and canal, east and northeast to Bois du Cabaret, 800 meters northeast of the Boise de Malakoff. The next day the command passed to the Australian 5th Division, but units of the 30th (US) Division, which were in line, participated until noon.
During its advance of , the 30th (US) Division captured 98 officers, 3,750 enlisted men, 72 pieces of artillery, 26 trench mortars and 426 machine guns. It suffered 8,415 casualties.
On 1 and 2 October 1918, the 117th Infantry Regiment as part of the 59th Infantry Brigade, 30th (US) Division moved to the Heroecourt and Mesnil-Bruntel Areas, and on the 5th, the II Corps prepared to relieve the Australian troops in the front line. Returning to the front the 117th Infantry as part of the 59th Infantry Brigade and other units moved to the Tincourt-Boucly Area.
On the night of 5 and 6 October 1918 the 59th Infantry Brigade took position in support near Hargicourt and Bellicourt. The next day the 59th Infantry Brigade attacked to realign the front.
The 30th (US) Division on 8 October, assisted by tanks had the 59th Infantry Brigade and one battalion from the 60th Infantry Brigade, leading, attacked northeast, and captured Brancourt-le-Grand and Premont, and reached a line from the Fme de la Piete to the eastern outskirts of Premont. The 6th (GB) Division served on the right, while the 25th (GB) Division was on the left. The 60th Infantry Brigade passed through the 59th on 9 October, and captured Busigny and Becquigny. The next day the division front extended along the western outskirts of Vaux-Andigny, through La Haie-Menneresse, and St. Souplet, to St. Benin.
During this advance on 7 October 1918 Sergeant Edward R. Talley, from Russellville, Tennessee, Company L, 117th Infantry Regiment near Ponchaux, France, was undeterred by seeing several comrades killed in attempting to put a hostile machinegun nest out of action. He attacked the position single-handed, armed only with his Springfield 03 rifle. Sergeant Talley rushed the machinegun nest in the face of intense enemy fire, killed or wounded at least 6 of the crew, and silenced the gun. When the enemy attempted to bring forward another gun and ammunition Sergeant Talley drove them back by effective fire from his rifle. For this action, he was awarded the Medal of Honor.
The next day, Sergeant James Ernest Karnes from Knoxville, and Private Calvin John Ward from Morristown, Company D, 117th Infantry Regiment near Estrees, France, on 8 October 1918 were taking part in a general advance. Their company was held up by a machinegun, which was enfilading the line of troops. These two soldiers "had all they could take" so they fixed their bayonets and charged the machine gun position and succeeded in destroying the machine gun nest by killing 3 and capturing 7 of the enemy and their guns. Sergeant Karnes and Private Ward were both awarded the Medal of Honor for this action.
On 11 October, the 30th (US) Division occupied Vaux-Andigny, La Haie-Menneresse, and reached the northwestern outskirts of St. Martin-Riviere, its front extending north along the West Bank of the La Selle River to St. Benin. It was relieved during the night of 11/12 October and 1918 by the 27th (US) Division, and rested near Premont, Brancourt-le-Grand, and Monibrehain. Command passed on 12 October 1918.
The 30th (US) Division returned to the line on the night of 15/16 October 1918. The 59th Infantry Brigade relieved the 54th Infantry Brigade (27th Division), in the right sector of the II Corps from Vaux-Andigny to one-half kilometer west of St. Martin-Riviere. The 6th (GB) Division on the right, 27th Division (US) on the left. On 17 October 30 (US) Division attacked northeast, crossing the La Selle River, captured Molain and established a line from three-quarters kilometer north of La Demi-Lieue to l'Arbre-de-Guise. The next day Ribeauville was occupied. The front extended from Rejet-de-Beaulieu to three-quarters kilometer southeast of la Jonquiere Fme, on 19 October 1918.