D Company at Bong Son — September 19, 1966 (Death of 2LT Derosier; LTC Tackaberry's Distinguished Service Cross)

September 19, 1966 — a patrol pinned down near Bong Son

Confirmed and well-documented. This action is recorded in detail in the Distinguished Service Cross citation of LTC Thomas H. Tackaberry, commander of 2nd Battalion, 8th Cavalry — the rare case in this archive where a single day's contact survives in a full first-order narrative. What is not yet pinned is the exact grid and the identities of the other men in the patrol.

On 19 September 1966, during Operation Thayer I (the 1st Cavalry Division's search-and-destroy operation in Binh Dinh Province, 13 September – 1 October 1966), a fifteen-man patrol of D Company, 2nd Battalion, 8th Cavalry was caught in an intense firefight with a reinforced company of the North Vietnamese Army near Bong Son. At approximately 1500 hours the patrol's platoon leader — 2LT Michael Douglas Derosier, 23, of Fort Walton Beach, Florida — was killed by small-arms fire, and the patrol was pinned down and in danger of being overrun.

The battalion commander's intervention

What happened next is the substance of LTC Thomas H. Tackaberry's second Distinguished Service Cross. From the citation (HQ U.S. Army, Vietnam, General Orders No. 6537, 28 November 1966):

"...At approximately 1500 hours a fifteen man patrol was engaged in an intense fire fight with a reinforced company of the North Vietnamese Army. The platoon leader had been killed and the patrol was pinned down. Lieutenant Colonel Tackaberry ordered his unarmed command helicopter to land near the action. Running through the intense fire, he reached the besieged patrol and assumed personal command of the unit. He then called for a reserve force to reinforce his position... he personally led the assault on the forward hostile bunkers and succeeded in driving the insurgents from their positions... Receiving word to extract his force, the patrol quickly returned to the landing zone and established a defensive perimeter. Two of the pickup helicopters were hit by intense fire from the rapidly regrouping hostile troops. Despite the threat of an all out insurgent assault on the landing zone, Lieutenant Colonel Tackaberry refused to leave until the rest of his men had been extracted. Along with two remaining soldiers, he dauntlessly continued to fire on the advancing hostile troops until being picked up by the unarmed command helicopter."

Tackaberry — who had taken command of 2/8 Cav only seven weeks earlier, on 30 July 1966 — went on to become one of the most decorated soldiers in U.S. Army history (three Distinguished Service Crosses, five Silver Stars) and retired a lieutenant general. This was his second DSC; the platoon leader whose death set the action in motion was 2LT Derosier.

2LT Michael Derosier

Michael Douglas Derosier was a 23-year-old platoon leader (MOS 1542, Infantry Unit Commander) who had arrived in Vietnam on 3 July 1966, ten weeks before his death. He is the only 2/8 Cav officer killed on 19 September 1966, which identifies him as the platoon leader the citation describes. He is buried at Arlington National Cemetery; his name is on the Wall at Panel 10E, Line 117. See his profile.

A note on the record: Derosier's official casualty file lists the province as Quang Tin (I Corps), but that is an error — 2/8 Cavalry was operating in Binh Dinh near Bong Son on this date, and the DSC citation places the action there. The Binh Dinh / Bong Son location is followed here.

What's still open

The detailed valor narrative survives, but the unit record does not yet: the exact grid, the other members of the fifteen-man patrol (the citation makes clear there were further casualties), and the enemy regiment all await the 2/8 Cav daily staff journal (NARA RG 472) and the Operation Thayer I after-action report.

Help us complete the record

If you served with D Company, 2/8 Cavalry during Operation Thayer I, or knew 2LT Michael Derosier, please reach us through the contribute form.