A wire screen protects this M113. The crew can take cover in their bunker. (111-CC-64235)
Each infantry division had an Armored Cavalry Squadron responsible for reconnaissance, intelligence gathering and security missions. (Note: The cavalry squadron was the equivalent of an infantry battalion, while the cavalry troop equated to an infantry company; both arms used the term platoon.)
DIVISION SQUADRON: 1st Infantry 1/4th Cavalry, 23d Infantry 1/1st Cavalry, 4th Infantry 1/10th Cavalry, 25th Infantry 3/4th Cavalry, 9th Infantry 3/5th Cavalry, 101st Airborne 2/17th Cavalry, 1/1st Cavalry served with Task Force Oregon before joining 23d Division
The squadron had twenty-one officers, two warrant officers and 240 enlisted men organized into a headquarters troop and three armored cavalry troops, A, B and C. The troops were equipped with M113A1 armored personnel carriers (APCs) for reconnaissance and M48A3 tanks (replaced by the M551 Sheridan) for firepower. Troop D was an Air Cavalry Squadron armed with observation, transport and helicopter gunships for aerial reconnaissance.
The headquarters troop rode in six M577 command carriers and ten M113 personnel carriers; four M132 flamethrower carriers dealt with bunkers. Ten 6-ton cargo carriers distributed ammunition while two M88 recovery vehicles and three 5-ton wrecker trucks recovered disabled vehicles. Ten 5-ton, fifteen 2½-ton, seven ¾-ton trucks and eighteen ¼-ton utility trucks provided transport.
THE ARMORED CAVALRY TROOP
The Troop was organized into a headquarters and three platoons and although organization often varied, it had around five officers and 192 enlisted men. Twenty-two M113s acted as command vehicles and personnel carriers. Nine M48 tanks gave direct close support while three M125 81mm mortar carriers gave indirect support. Transport was provided by one 2½-ton, one ¾-ton and three ¼-ton utility trucks; an M88 recovery vehicle recovered damaged vehicles.
The troop headquarters had four M113s. A captain ran his troop from the headquarters (APC) while the forward artillery observer, a lieutenant, kept in contact with the divisional artillery through the radio operator. The crew of the communications APC controlled the radio net while two radar APCs could set up ground surveillance radar to cover the troop’s perimeter.
Each platoon was led by a lieutenant and he led six M113s, one mortar carrier and three tanks. The scout section had four APCs organized into two squads to locate targets, so the tank section and the infantry APC could move in to engage it, while the mortar APC gave indirect fire support or fired smoke.
In action the driver continued to operate the M113 while the vehicle commander fired the .50-cal M2 and the two observers fired the M-60 machine guns (one acted as loader if he had no targets on his side). Each crew member had an M16 rifle and the vehicle carried an M79 grenade launcher. The platoon usually rode on and fought from their vehicles, however, the infantry APC carried a squad to search inaccessible areas. The M125A1 81mm Mortar Carrier provided indirect fire support for the platoon.
The tank section had three M48A3s and it was led by the lead tank’s commander; his two tanks were controlled by tank commanders. All three tanks had a driver, a gunner and a loader. The M48s were replaced by the lighter and faster M551 Sheridan, starting in 1969.
Mines were a constant worry for the cavalry troop and the APC crews often reinforced the floor of their vehicles with sandbags. Four-man engineer teams were often assigned to each troop to sweep for mines.
Each troop had a medic team when it was on operations and they either rode with the radar M113s or the squadron loaned them an M113 as an armored ambulance. A casualty clearing station would usually be set up next to the communications M113 so the medics could call in helicopters to retrieve the wounded.
The commander of an M113 receives new orders as it breaks through the undergrowth during one of 4th Division’s operations in the Central Highlands. (111-CC-59146)
The M113, and its variants, was a lightweight aluminum armored personnel carrier and its low ground pressure allowed the carrier to operate in many areas of South Vietnam, even during the monsoon season. It was able to cross paddy dikes and small streams, while crews were trained to recover their vehicles with winches, cables and beams. The M113s gave squads greater mobility while the armor protected anyone inside from small arms fire and shell fragments. However, the carriers were vulnerable to mines and men often preferred to sit on top of their vehicle rather than sweat it out inside. Some squads stacked sandbags inside to absorb an explosion but the added weight reduced speed and range.
The standard M113 was armed with a 12.7mm [50 Caliber M2] machine gun and a 7.62mm [M60] machine gun and it could carry up to 2,000 rounds of ammunition. It was 4.46m long, 2.33m wide, 2.16m high and weighed nearly 11.5 tons. The gas (petrol) engine in the A1 version had a maximum speed of 40mph but they were vulnerable to enemy fire and most M113s in Vietnam were the A2 variant fitted with a diesel engine.
Several M113 variants were deployed and the body of the M577 command variant was higher to allow the staff inside to work at map tables and operate their communications equipment while the M114A1 reconnaissance version was smaller and only weighed 7.5 tons; the unarmed M548 cargo carrier could carry up to 6 tons of equipment or ammunition for the rest of the platoon. Two variants carried mortars for providing indirect support. The M125A1 variant was armed with a 81mm mortar and it had an effective range of 3,650m. The M106A1 was armed with the heavier 107mm (4.2in) mortar with an effective range of 5,500m. A variety of field modifications were made to the M113 to suit the conditions in Vietnam, including a portable scissor bridge and fire-fighting equipment.
UPGRADING THE M113
Once it became clear that the M113 was as effective fighting vehicles, upgrade kits were deployed to armored cavalry units. Gun shields, pintle mounts and hatch armor gave the crew extra protection. Kit A allowed a .50in machine gun to be fitted to the commander’s cupola and two 7.62mm [M60] machine guns either side of the troop compartment. Modified versions allowed miniguns, recoilless rifles or grenade launchers to be fitted above the commander’s cupola. Kit B fitted a .50mm [50 Caliber M2] machine gun mounting to the mortar variants.
M551 ARMORED RECONNAISSANCE VEHICLE (SHERIDAN)
The M551 was a high-speed, yet heavily armed, armored reconnaissance vehicle capable of operating in swampy areas. It was developed to replace the heavy M48 tanks operating with the divisional and regimental cavalry squadrons (11th Armored Cavalry continued to use their M48). The main weapon, a 152mm M81 gun/missile launcher, was equipped with advanced night-vision equipment; the tank also had a .50in [50 Caliber M2] machine gun and a 7.62mm [M60] machine gun. The tank had a four-man crew and the diesel engine had a maximum speed of 43mph. It was 6.30m long, 2.79m wide, 2.95m high and weighed 16.7 tons.
The first Sheridans were delivered to 3rd Squadron, 4th Cavalry and the 1st Squadron, 11th Armored Cavalry Regiment in 1969 but confidence in the new tank was undermined when a mine ruptured the hull and detonated the ammunition inside one. There were reliability issues with the missile electronics and the caseless ammunition but the combination of the night sight and the 152mm canister round proved to be effective. Over 200 Sheridans were in action by the end of 1970.