On December 11, 1967, two Marine provisional rifle platoons moved in on a North Vietnamese Army (NVA) position near the mouth of the Cua Viet River. An attached company of Marine infantry had spotted an NVA platoon the day before. Part of Company B, 1st Marine Amphibious Tractor Battalion, the Marines pursued and now the battalion commander, Lieutenant Colonel Edward Toner, was ready to strike. Backing up Toner’s riflemen was a pair of LVTH-6 amphibious tractors mounting 105mm howitzers. Four more of the cannon-carrying vehicles, dubbed “H-6s,” were available for traditional indirect artillery fire support.
The attack began and ended with success. The two H-6s poured fire into the NVA troops, who desperately counterattacked. At times the range was as close as 50 meters. The other four H-6s added their weight to the fight and, when it was over, the Marines had suffered 20 wounded, but 54 NVA lay dead.
The Cua Viet fight demonstrated the versatility of the LVTP-5 series vehicles used by the Marines in Vietnam. Originally designed to shuttle Marines and equipment from ship to shore during amphibious assaults, the vehicles performed many other duties in Southeast Asia, including work as armored personnel carriers, as assault guns, engineer vehicles and recovery vehicles. The LVTP-5 did all this despite a dangerous design fault that made most Marines reluctant to ride inside it.
The Marine Corps’ LVTP (landing vehicle, tracked, personnel) series of amphibious tractors—called “amtracs”—was a continuation of the famous World War II personnel carriers. Amtracs had been used in the island-hopping campaigns of the Pacific Theater with great success. When the Korean War broke out in 1950, amtracs were used during the Inchon landings and elsewhere. In Vietnam, French forces used American-supplied amtracs in their operations against the Viet Minh.
During the Korean War, development began on a new vehicle to replace the aging amtracs. In 1950 a contract was awarded to the Borg-Wagner Corporation’s Ingersoll Products Division to develop the new LVTP-5 and its variants. A prototype was ready in August 1951, and testing went forward. Production began in 1952, but the rushed developmental period resulted in a number of mechanical problems that delayed the vehicle’s entry into service until 1956, followed by more testing with Marine units that exposed additional problems. The vehicles ultimately modified to reduce these mechanical problems were given the “A1” designation, added to the end of the model number.
Though not off to a good start, the LVTP-5 was capable of performing its intended mission—that of putting Marines onto the beach. Weighing in at 64,200 pounds, the massive vehicle was powered by an 810-HP Continental LV-1790-1 V12 engine that gave it a land speed of 30 mph and up to 6.8 mph in the water. Ashore, the LVTP-5 had a range of 190 miles; in water, 57 miles. With a three-man crew, it was designed to carry 34 troops in the hull, but in practice, the normal maximum was about 25 Marines with combat equipment. The vehicle’s armor topped out at six-tenths of an inch thick, and a cupola on top mounted a .30- caliber machine gun.
Variants to the troop-carrying model included the LVTH-6, the “H” standing for howitzer. It mounted an M49 105mm howitzer in a turret atop the hull. Up to 151 rounds of ammunition could be carried on board on land, but when it was waterborne, no more than 100 rounds were stowed to keep the vehicle balanced. Another version was the LVTC, a command vehicle for headquarters elements. A recovery and repair vehicle using the same hull was called the LVTR-1. An engineer vehicle, the LVTE-1, weighed 82,750 pounds and could be fitted with a bulldozer blade. The dozer blade also had a rake-like device for use in mine clearing, and on its roof was mounted a rocket-propelled demolition charge. The rocket could be launched across a suspected minefield, trailing a line charge of explosives. Once laid across the minefield, the line charge detonated, clearing a path. An antiaircraft LVTP-5 variant was developed, but because of problems in testing, it never entered production. By 1957 a total of 1,112 LVTP-5s had been produced, along with 210 LVTH-6s, 55 engineer variants, 65 recovery vehicles and 58 command versions of the amtrac.
These vehicles were assigned to Marine amphibian tractor battalions, with each battalion having 120. A standard platoon had 11 LVTP- 5A1s, with four platoons making up a company and two companies in the battalion. The remaining amtracs were assigned to the company and battalion headquarters, and those were mostly command vehicles or engineer and recovery variants. Each Marine division had an assigned amphibian tractor battalion. The 1st and 3rd Amphibian Tractor battalions served in Southeast Asia.
Once ashore, the LVTP-5s experienced hard use and their shortcomings became apparent, as they had been designed primarily to ferry Marines from ship to shore, including landings on contested beaches against defending enemies. They could operate inland, but Vietnam’s rough terrain taxed the suspension system in particular. Maintenance was always a challenge with the LVTP-5, and hard use on land strained its problematic mechanical systems. The crew could easily be kept busy just pulling daily maintenance, and replacing an engine or transmission often required an entire day.
The second and more lethal problem for the LVTP-5 was its vulnerability to mines. The VC and NVA were skilled at adapting various explosives into impromptu mines using artillery shells, aircraft bombs and whatever else could be salvaged or scraped together. Normally a vehicle as big and heavy as the LVTP-5 would have some resistance to such devices, but the amtrac’s fuel tanks were installed in its floor: 12 cells carrying up to 456 gallons of gasoline. Hit a mine, and the vehicle’s fuel supply would often go up in flames, with horrific results for anyone trapped inside. A lucky crewman would be blown clear of the amtrac by the explosion; otherwise he would be burned to death. Most Marines, therefore, preferred to ride on the top of the vehicle, stacking sandbags around the amtrac’s roof to provide some protection.
Another hazard stemmed from the fact that the LVTP-5’s cupola-mounted machine gun was designed to spray an enemy-held beachhead with fire from the water, so the gun could not be depressed very far, resulting in some dead space close-in to the vehicle. Once Marines started riding atop their amtracs, the machine gun was often blocked by the men or the sandbags. To address that, the machine gun would some times be mount ed over the sandbags so it had a clear field of fire.
All these drawbacks limited the LVTP-5’s effectiveness as a personnel carrier, but without additional land-oriented vehicles, such as the Army’s M113, the Marines had to make do with what they had. As the Marines on the ground learned how to better fight their enemy, the amtrac was utilized less as a strict combat personnel carrier—but it was still widely used in a range of support roles, such as ferrying supplies back and forth, often escorted by tanks.
The LVTP-5 was better adapted to riverine and “brown-water” operations. The Marine Corps formed several special landing forces, using them to patrol navigable rivers and coastlines. The VC and NVA generally steered clear of areas where these special landing forces operated.
The recovery amtracs were always in demand to retrieve other armored vehicles disabled in combat. They also were used to tow broken-down vehicles or ones stuck in Vietnam’s often soft and boggy ground. The howitzer carriers were intended mainly for indirect fire support, just like regular artillery, but were often deployed as a substitute tank to support infantry. One such unit, the 1st Provisional Armored Amphibian Tractor Platoon, was established for a six-month trial in 1965. It wound up serving in Vietnam until 1972, supporting a South Korean Marine Brigade. It fired more than 200,000 rounds of 105mm ammunition during its combat service.
After Vietnam, the LVTP-5 was replaced by the LVTP-7, which was improved based on the lessons from Vietnam, becoming smaller, lighter and much more durable for use on land. It continues in service today as the AAV-7.
Originally published in the October 2008 issue of Vietnam Magazine. To subscribe, click here.