The M551 Sheridan also went by the designation of the AR/AAV, or Armored Reconnaissance/Airborne Assault Vehicle. But it was actually an Army light tank. It was amphibious and could swim rivers at 3-4 mph. The most interesting thing about the Sheridan was that it could be dropped by parachute, which gave it a much longer service life as the only organic armor in the 82nd Airborne Division.
The Sheridan was named after General Philip Sheridan, the Union’s outstanding cavalry commander during the Civil War. During the war, Sheridan rose from 1st Lieutenant to Major General, a meteoric rise for a legend of the US Cavalry.
His Shenandoah Campaign of 1864 destroyed the “breadbasket” of the Confederacy, one of the first uses of “scorched earth” policies in the war.
Originally designed as an armored reconnaissance vehicle for cavalry units, it saw extensive action in Vietnam and has a checkered history there.
Background of the M551 Sheridan’s Use in Vietnam
In 1968, General Creighton Abrams, the new commander of US troops in Vietnam, was prepared to replace the heavier M48A3 Patton tanks in the Cavalry units with the Sheridan.
“In late 1968, General Abrams met with Colonel George S. Patton IV (son of WWII General Patton, and Abrams’ commander), commander of the 11th Armored Cavalry Regiment (11 ACR).
“When Abrams mentioned the cavalry’s concerns over the new vehicle, Patton recommended that the M551s be combat tested by a divisional cavalry squadron as well as a squadron from his own regiment since the two squadrons had completely different missions,” from the outstanding history of the Sheridan by Mike’s Research.
Another outstanding article on the Sheridan in Vietnam was written by Dale Dye, who played Colonel Sink in Band of Brothers. He is a historian with impeccable credentials. Hardly a war film gets made without his involvement as a technical advisor. He was a captain in the Marine Corps but was an Advisor with the Army in a South Vietnamese (ARVN) Armored Cavalry Unit.
Dye learned armor tactics on the job, and by his account, he loved it. His first experience with “sort of” tank was with “the relatively new M551 Sheridan, which had only just arrived in Vietnam at the first of the year (1969). It was a hotrod by armor standards, powered by a supercharged six-cylinder Detroit Diesel and capable of around 50 mph on a flat surface with a tailwind.”
“The Sheridan was sleek and had a futuristic look with a cool saucer-shaped turret mounted on a vehicle that weighed in at just 16-plus tons. It seemed most things in the Army’s vehicle inventory in those days had to be light enough to drop along with paratroopers in airborne operations. None of the advisors in our outfit had ever seen a Sheridan dropped by parachute.” (I have, and it is incredible.)
“The infantry loved the Sheridan’s M265 canister round, an updated version of the venerable battlefield favorite Beehive. The Sheridan’s canister rounds were the money shots in Vietnam.” The canister round was used against enemy troops in close quarters as it fired 1,000 flechettes to devastating effect.
Pros of the M551 Sheridan
It was more mobile than the M-48 Patton tanks, better armored than the M113 armored personnel carriers it was replacing, had good cross-country mobility, and was fast. The Sheridans could race on roads at nearly 50 mph. Cadillac made it. So, what young tanker wouldn’t want to tool around Vietnam with a Caddy that touted a 152mm main gun?
The Sheridan did pack a punch. Its M81E1 Rifled 152-mm main gun carried 20 rounds and eight to nine MGM-51 Shillelagh missiles. This armament could defeat any known armor and destroy bunkers and built-up positions. The weapon also fired M625 canister rounds loaded with thousands of flechettes, which decimated light Viet Cong infantry during the battles of Tay Ninh and Bien Hoa.
The M551 also carried a .50 caliber heavy machine gun and a 7.62mm GPMG in the turret.
Cons of the M551 Sheridan
Troops distrusted the Sheridan before it arrived in South Vietnam because of its lack of armor. The hull was made of aluminum and was very thin. The turret was made of steel, but it, too, didn’t have thick armor. Therefore, the Sheridan was highly vulnerable to anti-tank mines and rocket-propelled grenades, which were the favorite weapons of the Viet Cong and North Vietnamese regulars.
The vehicle also had a significant issue with 152 mm ammunition. The round was attached to the propellant charge, which was combustible, and many times, the projectile separated from the combustible case during loading. Therefore, the tank’s crewmen were trained not to load the round.
Because the highly combustible propellant charge was held inside the turret, the crews were trained at the first sign of fire or smoke inside the tank; the crew was to abandon the vehicle.
The Sheridan’s rate of fire could have been faster: only about two rounds per minute, while a well-trained M48 crew could fire 18-19 rounds per minute. Another issue was that the tank was light (15 tons). When the main gun was fired, the front of the tank rocked upward, and many times, the commander in the open hatch was injured by the hatch ring when rocking backward.
In Vietnam, as Captain Dye points out, it was a “Noble but Doomed” cause.
The Army began phasing out the Sheridan, except for the 82nd Airborne Division, which was the sole organic armor support the division would use in combat. And they did just that in 1989.
The Sheridan Parachutes Into Panama, 1989
The Army began phasing out the Sheridan in 1978, but the 82nd Airborne had a use for them as deployable armor for the division. In 1988, when the 82nd deployed to Honduras during Operation Golden Pheasant, Sheridans were deployed but airlanded during the brief Nicaraguan invasion.
In 1989, however, the Sheridan earned its combat jump wings. During the invasion of Panama, the 82nd jumped at Tocumen airport. That’s where 10 Sheridans were airdropped via C-141 Starlifter aircraft. These were part of C Co. 3/73 Armor. Four others were secretly brought in before the invasion via C-5 Galaxy aircraft at Howard Air Force Base.
The Sheridans received high marks in Panama due to the Panamanian military having primarily small arms and generally having no stomach for the fight against armor.
The Sheridan was deployed in Operation Desert Shield/Desert Storm in 1990-91. Due to its thin armor, it saw action but was limited to a flanking reconnaissance role. There, it fired the Shillelagh missiles for the first and only time in combat. Once again, Sheridan tanks received high marks.
The Army found use for the Sheridans at the Joint Training Center at Ft. Irwin, CA. The Army modified the Sheridans to resemble T-72s, BMPs, and ZSU-23-4s. They became weapons of the OPFOR in training. As anyone who went there, the OPFOR were formidable opponents.
Retirement
The Sheridan was finally retired from the 82nd Airborne in 1996. No replacement has yet been adopted for the Sheridan, and the light airborne division could use one. But for now, the paratroopers are using Javelin missiles for anti-tank defense.
M10 Booker: The ‘Light Tank’ That Almost Made It
Members of the North Carolina Air National Guard assess an Army M10 Booker Combat Vehicle before it is loaded onto a C-17 Globemaster III aircraft, at the North Carolina Air National Guard base, Charlotte-International Airport, August 3, 2024. Portions of this photo were masked for security reasons. (U.S. Air National Guard photo by Staff Sgt. Reanna Hartgrove)
The M10 Booker displayed at it’s dedication ceremony at Aberdeen Proving Ground in Aberdeen, Md., April 18, 2024. As part of the dedication of the M10 Booker Combat Vehicle in their name, Pvt. Booker, a Medal of Honor recipient, and infantryman, assigned to the 133rd Infantry Regiment, 34th Infantry Division, during World War II, and Staff Sgt. Stevon A. Booker, a Distinguished Service Cross recipient, and tank crewman, assigned to Alpha Company, 1st Battalion, 64th Armor Regiment, 3rd Infantry Division, in support of Operation Iraqi Freedom, will be recognized and honored for their ultimate sacrifice, heroism and commitment to service and the country, represented by family members during the ceremony. (U.S. Army photo by Christopher Kaufmann).
M10 Booker is part of a static display while a live segment for FOX and Friends is being filmed at Fort Liberty, N.C., May, 21, 2024. The M10 Booker Combat Vehicle is named after two American service members: Pvt. Robert D. Booker, who posthumously received the Medal of Honor for actions in World War II, and Staff Sgt. Stevon A. Booker, who posthumously received the Distinguished Service Cross for actions during Operation Iraqi Freedom. Their stories and actions articulate the Army’s need for the M10 Booker Combat Vehicle, an infantry assault vehicle that will provide protection and lethality to destroy threats like the ones that took the lives of these two Soldiers. (U.S. Army Photo by Sgt. Jacob Bradford)
PD1 – Delivery of First Production Vehicle M10 Booker Combat Vehicle
M10 Booker Light Tank. Image Credit: Creative Commons.
About the Author
Steve Balestrieri is a 19FortyFive National Security Columnist. He served as a US Army Special Forces NCO and Warrant Officer. In addition to writing for 19FortyFive, he covers the NFL for PatsFans.com and is a member of the Pro Football Writers of America (PFWA). His work was regularly featured in many military publications.
