A History of the 5th Infantry Division in Vietnam
- Jim Broumley
- Nov 13, 2025
- 3 min read
Updated: Jan 9
A History of the 5th Infantry Division in Vietnam
The U.S. Army’s 5th Infantry Division (Mechanized) has the nicknames of "Red Devils" or “Red Diamond" for the simple design of their shoulder sleeve insignia, a red diamond. The 5th Infantry Division is currently inactive. But the Red Diamond has a superior combat record from the First World War, World War II, Vietnam, and Operation Just Cause, the invasion of Panama.
This blog is a short history of the 5th Infantry Division during the Vietnam War, or you can click on the image below to see the video version:
After the Second World War, the Red Diamond Division was inactivated and reactivated several times to respond to the country’s security needs. By the mid-1950s, the Red Devils were part of NATO forces stationed in West Germany as part of the United States' Cold War defense of Europe. The 1960s found the 5th ID stationed at Fort Carson, Colorado. On March 25, 1968, the 1st Brigade, 5th Infantry Division (Mechanized) was alerted for deployment to Vietnam.
To make the Red Devil's 1st Brigade combat effective as a separate maneuver unit, there were a few new assignments and attachments. When finished, the Brigade consisted of three infantry battalions, one armor battalion, a mechanized cavalry troop, an artillery battalion, a company of engineers, and various supporting detachments that included the 43rd Scout Dog Platoon. In February 1969, the 1st Brigade, 5th Infantry Division (Mech) was assigned operational control of the 3rd Squadron, 5th Cavalry. Charlie Troop, 3rd of the 17th Air Cavalry, was placed under the operational control of the Red Devil Brigade in the summer of 1970. At its peak strength, this separate brigade had over 6,000 personnel assigned and was one of the most potent fighting forces in the Republic of Vietnam.
Initially, the Red Diamond Brigade conducted a 13-week training and familiarization program to adjust the brigade's personnel to what they would face in Vietnam. The emphasis was on small unit tactics and rapid response to alerts. In June 1968, the brigade began the long movement overseas. The advance party arrived in Quang Tri on July 2, 1968. The remainder of the Brigade arrived by July 22. The 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 Red Diamond Brigade to be tactically committed. On August 12, 1968, the unit moved north to Con Thien to support the 1st Marine Regiment for ten days in their fight with NVA 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.
The Red Devils continued to operate in an area known as "Leatherneck Square," assisting the 3rd Marine Division in denying access to the south through the DMZ. During April and May 1969, the Red Diamond Brigade worked 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 stop the movement of communist tax collectors.
In August 1969, the Red Devils assumed full responsibility for "Leatherneck Square” as the Marines withdrew from that area. After six weeks of constant activity, the brigade was removed from the operational control of the 3rd Marine Division. Now part of XXIV Corps, they and the 1st ARVN Division had sole responsibility for the defense of Quang Tri and Dong Ha combat bases.
In January 1971, the reinforced 1st Brigade, 5th Infantry Division, initiated Operation Lam Son 719. The Brigade opened Route Nine from Dong Ha to the Laotian border. Then a 20,000-man ARVN Task Force moved to the Laotian border. The Red Diamond Brigade secured Highway nine as a supply route and provided mobile defense for the huge forward support area of Vandergrift and Khe Sanh. For 69 days of bitter fighting, the Red Devils prevented the enemy from making a successful offensive move against these vital supply links in the ARVN offensive.
In June 1971, the Red Devils received stand-down orders with stateside redeployment to commence on July 1. The Brigade colors departed Quang Tri on August 8, 1971, after a ceremony the previous day in which several Vietnamese decorations were awarded to the Brigade and to Brigade personnel. The Red Devils returned to Fort Carson, leaving the defense of Quang Tri in the hands of the ARVN 1st Division, a unit that they had largely trained. On August 22, 1971, the Brigade colors were cased at Fort Carson, Colorado. The Red Diamond was inactive once again. Through the efforts of the unit soldiers, the Red Devils, the 5th Infantry Division, earned its motto: "We will."
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