The 5th Division achieved worldwide recognition for its valor, proficiency and determination. The 1st Brigade was alerted for deployment to Vietnam on 25 March 1968. Considerable tailoring had to be done in order to make it combat effective as a separate brigade. In addition to Headquarters and Headquarters Company, 1st Brigade, 5th Infantry Division (Mechanized); the following units were assigned: 1st Battalion, 11th Infantry; 1st Battalion, 61 Infantry (Mechanized); 1st Battalion, 77th Armor; A Troop, 4th Squadron, 12th Cavalry; 5th Battalion, 4th Artillery; 75th Support Battalion; A Company, 7th Engineers; 298th Signal Company; 517th Military Intelligence Detachment; 86th Chemical Detachment; 48th Public Information Detachment; 407th Radio Research Detachment; and 43d Scout Dog Platoon. On 24 February 1969 the 1st Brigade, 5th Infantry Division (Mech) was assigned operational control of the Third Squadron, Fifth Cavalry. Charlie Troop, 3rd Squadron, 17th Air Cavalry was assigned under the operational control of the Red Devil Brigade in the summer of 1970. At peak strength the brigade had over 6,000 personnel assigned and was one of the most potent fighting forces in the Republic of Vietnam.

Initially commanded by Colonel Richard J. Glikes, the Brigade conducted a 13-week training and familiarization program to adjust the brigade's personnel to situations in Vietnam. The emphasis was on independent small unit tactics and rapid response to alerts. In June 1968, the brigade began the long and difficult overseas movement. The advance party arrived in Quang Tri base on 2 July 1968. The remainder of the Brigade had closed on Quang Tri by July 22, and three maneuver battalions were located at separate base camps outside Quang Tri base proper.

A Company, 1st Battalion, 77th Armor, was the first unit of the Brigade to be tactically committed. On 12 August 1968, it moved north to Con Thien to support the 1st Marine Regiment for ten days against North Vietnamese Army units attempting to infiltrate through the demilitarized zone. A Company made five contacts was credited with 80 killed, and set the standard for the Brigade.

On 26 August, the Brigade moved into the area known as "Leatherneck Square", and the first operation in force was conducted there. While patrolling north of Con Thien on the 31st, D Company, 1st Battalion, 11th Infantry was hit with mortars. Spotting four NVA, the lead platoon pursued until they came under automatic weapons fire and additional mortars and artillery fire. The enemy was well dug-in and succeeded in pinning down the point squad. A platoon from C Company, 1-11 and four tanks from C Company 1-77 joined the battle. Attacking the dug in enemy positions, the reinforced Red Devils overran the first line of defense, causing the enemy to rout and break contact. Elements of the 11th Infantry and 77th Armor overran a bunker complex later, counting 52 North Vietnamese Army bodies. Throughout the next two months, the Brigade conducted battalion-size operations in and around the demilitarized zone. On almost every occasion, the firepower and mobility provided by the Brigade's tanks and APCs routed the enemy, inflicting substantial casualties while sustaining minimal losses to the Brigade.

Between 23 and 26 October 1968, the 1st Battalion, 61st Infantry and B Company, 1st Battalion, 77th Armor conducted a sweep into the demilitarized zone itself. The infantry was initially pinned down by heavy mortar and machine gun fire. The tanks were committed in a cavalry-like charge on the flank of the battle and routed the North Vietnamese out of their positions into the open, immediately inflicting very heavy casualties on the combined firepower of the two units. During the actions in four days, 303 enemy bodies were counted, 258 individual and 16 crew-served weapons were captured. Since the enemy always attempted to recover all weapons, this latter fact is most significant and indicated that the enemy was so routed as to be unable to retain the weapons. On 2 November 1968, the Brigade activities were moved back to an area of operation near Quang Tri City. This area of operation was eventually known as AO Marshall Mountain. In this area of operation, the Brigade conducted cordon and search operations with the 1st Regiment, 1st ARVN Division. By the end of February 1969, four months later, the Brigade had conducted 37 such operations. In addition to the cordon and search operations, the Brigade conducted routine patrols and established civic action programs. The Brigades provided transportation for refugees, construction materials, assisted in road building, and established medical aid visits to friendly villages.

On 28 February 1969, the recently assigned 3d Squadron, 5th Cavalry made contact west of Quang Tri. Conduct was maintained for two days, and three companies were committed to the assault. Eight battalions of artillery and the "16 inch" guns of the battleship "New Jersey" bombarded the enemy and his withdrawal route. First Brigade casualties were three killed and 35 wounded. Estimated North Vietnamese Army casualties were 118. The high proportion of wounded to killed was typical of US activity in Vietnam. The excellent medical services, communication facilities, and skillful helicopter evacuation saved countless US lives throughout the 1st Brigade's stay in Vietnam. On 16 March, the Brigade was committed to armor and mechanized infantry support of the 3d Marine Division in Khe Sanh Plain area. For three days, between 12 and 16 April, the Brigade conducted a search and clear operation over a 100-square kilometer area near Lang Voi on the Laotian border. No US were killed and North Vietnamese Army casualties were also light.

In April 1969, during an Operation Ellis Ravine, the Brigade conducted a search and clear operation while building a road into the Ba Long Valley. Task Force 3/5 moved into the valley from the west and Task Force 1/11 moved into it from the east while a road was built from Phuoc Mon to Ca Lu. Task Force 1/11 remained in the valley until the road was opened to traffic on 15 April.

Ten days later, the Ranger team of P Company, 75th Infantry ambushed and killed Nguyen Quyet, one of the major guerrilla leaders in Quang Tri Province. Quyet was a known Communist security chief, a terror and assassination cadre commander, and guerrilla band force leader. It was known that he had personally murdered several government officials and government supporting civilians. During April and May, the Brigade attempted to deny the enemy access to the rice harvest. To accomplish this, the Brigade provided security for the friendly populace as they harvested their crops and patrolled at night to inhibit the movement of North Vietnamese tax collectors.

In June, elements of the 1st Battalion, 61st Infantry and 1st Battalion, 77th Armor again combined with the Marines in the Khe Sanh area for operations against the North Vietnamese Army's 24th Regiment. The enemy body count totaled 147 and only light casualties as a result of nine days of action.

This emphasized the value of armored vehicles, even when the terrain is not suitable for their movement. The rice denial efforts continued in June. The area of operation moved to the east of Quang Tri, and this was coordinated with a Vietnamese Government pacification program. Throughout July the 1st Battalion, 61st Infantry and 1st Battalion, 77th Armor Task Force remained with the Marines, providing them with a mobile strike force and shock power as needed.

In August 1969, the Brigade assumed full responsibilities for "Leatherneck Square". For six weeks constant activity kept all units of the Brigade busy in this area. On 22 October, the Brigade was removed from the operational control of the 3d Marine Division and placed directly under the commanding general of XXIV Corps. In conjunction with the 1st ARVN Division, the Brigade now had sole responsibility for the defense of Quang Tri and Dong Ha combat bases.

As many patrols as possible continued, and from 11-18 November contact with the North Vietnamese Army's 27th Regiment was maintained by 1st Battalion, 61st Infantry and two companies of 1st Battalion, 77th Armor. By 20 November 1969, the North Vietnamese Army Regiment was in rapid retreat toward the Laotian border. The Brigade continued the rice denial patrols and to provide security for the Vietnamese Government pacification program.

CPT. Stanley A. Blunt, company commander of D Company, 1st Battalion, 11th Infantry, distinguished himself on November 11th and 13th of 1969 while leading his company during a search and clear operation through enemy controlled territory several kilometers south of the DMZ. On November 11th, his company was participating in a coordinated battalion attack on elements of the 27th NVA Regiment defending heavily fortified bunker positions. When his company's advance was halted by intense suppressive fire, CPT Blunt single-handedly charged and destroyed a heavily fortified machine gun position. In this assault he killed four other enemy soldiers at close range by hurling hand grenades into their positions. In the early morning hours of November 13, in a continuation of the same operation, CPT Blunt infiltrated a seven-man patrol through some twelve hundred meters of closely defended enemy terrain under cover of darkness to reinforce an extract besieged friendly elements. He conducted the mission without incident and undoubtedly saved the lives of the 22-trapped American soldiers. With few exceptions, during the entire first quarter of 1970, the Brigade saw light activity involving the pacification program and regional or popular forces. The exception was a Task Force of the 1st Battalion, 61st Infantry, which included three days of heavy combat. In fighting, which occasionally became hand-to-hand, 60 North Vietnamese were killed, and the North Vietnamese Army Command Post was overrun, and a large amount of equipment was captured.

In May 1970, D Company, 1st Battalion, 11th Infantry got the worst of an engagement when they were the perimeter security element for fire support base Fuller. They received 600 rounds of 120mm mortar fire without being able to make effective reply. In January 1971, a reinforced 1st Brigade, now under the command of BG John C. Hill, Jr., initiated operation Lam Son 719. The Brigade opened the QL9 Road from Dong Ha to the Laotian border; at he same time engineers constructed access roads from the Rock Pile through the Punch Bowl to Khe Sanh. Following this, a 20,000-man ARVN Task Force moved to the Laotian border. The 1st Brigade's missions were to secure QL9 as a supply route and provide mobile defense for the huge forward support area of Vandergrift and Khe Sanh. For 69 days of increasingly confused and bitter fighting, the brigade prevented the enemy from making a successful offensive move against any of these vital links in the ARVN offensive. A body count of 400 North Vietnamese was made, and the primary mission to keep the logistical support channels fully operational at all times was accomplished by the brigade. When the last of the logistical units had withdrawn, the 1st Brigade resumed its search and cordon patrols and rice denial efforts in eastern Quang Tri Province.

In June, the Red Devils received stand down orders with stateside redeployment to commence on 1 July 1971. BG Harold H. Dunwoody limited the Brigade activities to base security in anticipation of a North Vietnamese Army effort to achieve a propaganda victory over the departing unit. The Brigade colors depart Quang Tri on 8 August 1971, after a ceremony the previous day in which several Vietnamese decorations were awarded to the Brigade and to Brigade personnel.

The Brigade returned to Fort Carson, leaving the defense of Quang Tri in the hands of the ARVN 1st Division, a unit which it had largely trained. On 22 August 1971, the Brigade colors were inactivated at Fort Carson until the next call-up of the Division.

Vietnam Campaigns:

(8)   Vietnam Counteroffensive, Phase V, 1 July 1968 to 1 November 1968.
(9)   Vietnam Counteroffensive, Phase VI, 2 November 1968 to 22 February 1969.
(10) TET 69 Counteroffensive, 23 February 1969 to 8 June 1969.
(11) Vietnam Summer-Fall 1969, 9 June 1969 to 31 October 1969.
(12) Vietnam Winter-Spring 1970, 1 November 1969 to 30 April 1970.
(13) DA Sanctuary Counteroffensive, 1 May 1970 to 30 June 1970.
(14) Vietnam Counteroffensive, Phase VII, 1 July 1970 to 30 June 1971.