By late 1967, the M50 Ontos was just about phased out of military service. The Army had rejected it back in 1953, calling it too cramped, too lightly armored and too awkward to reload. Only the Marine Corps wanted it. Initially, they had no idea what to call the ugly machine. The military feared that giving it a traditional name of a famous general would offend someone.
The troops began referring to it as Ontos, Greek for “The Thing.” But after years of combat in Vietnam, the Marines were just about done with it. Parts were hard to find, and the treads wore out faster than they could be replaced. The few remaining vehicles were being cannibalized to keep other platforms running.
In December of 1967, the 1st and 3rd Anti-Tank Battalions were decommissioned. The few remaining Ontos vehicles were sent to support Marine Corps armor battalions elsewhere. Little did anyone know that the defining battle for the Marine Corps in Vietnam was about to begin.
By the end of the Battle of Hue two months later, Col. Stanley S. Hughes called the Thing "the most effective of all Marine supporting arms."
The Fall of Hue
On Jan. 30, 1968, eight battalions of the North Vietnamese Army infantry infiltrated Hue as part of the Tet Offensive. The attack caught American and South Vietnamese forces off guard during the Lunar New Year ceasefire.
The city was the cultural heart of Vietnam, home to the imperial palace and the seat of the Nguyen dynasty for over a century. For the NVA, taking Hue meant more than a military victory. It meant seizing the soul of Vietnam.
The 6th NVA Regiment seized the Citadel, an 18th-century walled fortress on the north bank of the Perfume River. The walls stretched 2 miles on each side, 16 feet high, and up to 60 feet thick at the base. The 4th NVA Regiment took the southern half of the city.
Within hours, the enemy controlled nearly all of Hue except for two compounds: the South Vietnamese Army's 1st Division headquarters inside the Citadel and the U.S. Military Assistance Command Vietnam compound south of the river.
Marine reinforcements arrived, expecting to quickly push out the enemy force. Instead, they found themselves fighting in some of the most vicious urban combat in American military history.
Street by Street
The NVA had turned Hue's concrete buildings into bunkers. They occupied upper floors and basements, cut firing holes through walls, and connected positions through mouseholes knocked between rooms. Snipers covered every approach. Machine guns created interlocking fields of fire down every street. Every intersection became a kill zone.
The Marines had no doctrine for conducting large-scale urban combat. According to the Marine Corps Vietnam Tankers Historical Foundation, tankers "had essentially no prior training or practical experience in the use of their 'crew-served weapon' in urban house-to-house, block-by-block, street-by-street fighting."
Neither did the infantry. The last time Americans fought in a city like this was in Seoul in 1950.
Air support and artillery were initially restricted to protect the civilians and historical sites. The Marines tried frontal assaults across open streets. They took heavy casualties and gained little ground. They needed something that could knock down walls at close range without leveling the entire city.
The Ontos Arrives
Ontos platoons and tanks from the 1st Tank Battalion reached Hue in the first days of February. The M48 Patton tanks weighed 50 tons and struggled in Hue's narrow streets. The Ontos weighed 9 tons. It could go where the Pattons could not, including cramped alleyways and over narrow bridges.
The Ontos mounted six 106mm recoilless rifles on a tracked chassis. The rifles vented their backblast out the rear, eliminating recoil and allowing the light vehicle to carry firepower normally reserved for much heavier platforms. The vehicle was originally designed as a light and maneuverable tank-hunter meant to tackle Soviet tanks in central Europe.
However, at ranges of 300 to 500 yards, those rifles could also punch 4-square-meter holes through masonry or knock down walls entirely. While the Pattons struggled to maneuver in some areas, the Ontos’ high-explosive rounds proved perfect for assisting the infantry in their assaults on fortified positions.
The Ontos also carried beehive rounds. Each round contained 9,600 flechettes, 2-inch steel darts with stabilizing fins that spread in a cone when fired. The darts made a terrifyingly distinctive buzzing sound as they shredded everything in their path.
Capt. Collin Casey commanded A Company, 1st Tanks at Hue. He described how the vehicles worked together.
"The Ontos was primarily used as a backup for the tank. We primarily used them in a hit-and-run type of thing," Casey said. "While they had great firepower, their armor was thin and could be penetrated quite easily by the NVA's weapons, so the Ontos was best employed by protecting them. It was primarily a building buster."
Instead of advancing down streets covered by NVA machine guns, the Marines used the Ontos to blast holes through compound and building walls. The infantry then entered the buildings without exposing themselves to crossfire.
If enemy snipers or machine guns halted the advance, the Marines were quick to call up an Ontos, which could quickly throw six projectiles into the enemy position. The stalemate began to break as the Marines slowly regained control over the city.
The Thing
Capt. Dale Dye, a decorated Vietnam veteran who later became a Hollywood military advisor, was at Hue during the fighting. In an account published in The Armory Life, he described watching Lt. Col. Ernest Cheatham, commanding officer of 2nd Battalion, 5th Marines, direct Ontos fire against the Citadel.
"I distinctly recall watching (from deep cover) as Lieutenant Colonel Ernie Cheatham ground-guided an Ontos right up to the riverbank and pointed at a spot on the Citadel walls that was hitting his Marines with flanking fire from across the river," Dye wrote. "There was some fiddling for position, then two spotter rounds, followed by ripple fire from a pair of 106s. A large chunk of wall fell into the moat surrounding the Citadel, and harassing fire from that direction ceased permanently."
Dye also witnessed the courage of Ontos crews. The vehicle's six rifles had to be reloaded from outside, one 38-pound round at a time, exposing the loader to enemy fire. The loader worked from a compartment in the back with just 18 rounds of ready ammunition. After a few salvos, someone had to go outside.
"One of the bravest guys I ever saw in combat was a skinny little PFC from Kansas," Dye wrote. "He was the loader on an Ontos, and several times in the fighting for Hue City during Tet 68, I saw him bolt out of his cubby hole in the back of that vehicle, ignoring incoming rounds pinging off the armor, to calmly reload."
The NVA learned to fear the Ontos. The backblast alone swept streets with dust, rocks, and debris that became deadly shrapnel. Survivors of the southside fighting had seen what six recoilless rifles could do to a fortified position. Word spread among the defenders.
Dye described what happened when Marines from Delta Company, 1st Battalion, 5th Marines were pinned inside the Citadel by an NVA platoon.
"They couldn't move forward or sideways, and going back was not an option," Dye wrote. "So an Ontos rolled up, threw ONE tracer from its .50 caliber spotting rifle into a window where most of the fire was concentrated, and the NVA abandoned it, scattering like cockroaches. The Ontos never even had to fire its 106's."
A single tracer round from a spotting rifle cleared an entire enemy position. The NVA knew what came next if they remained. The flechette rounds were especially feared by communist troops in the city.
"Apparently, the word had spread from NVA survivors of the southside fighting to their buddies on the northside," Dye wrote. "When The Thing rolls up on your position, it's time to un-ass the area."
Learning Under Fire
The Marines developed their tactics night by night. Patton and Ontos crews returned each evening to the South Vietnamese Army compound. They met with infantry squad leaders who had served as their eyes and ears during the day's fighting, providing security and guiding the armor through streets they could barely see from inside their vehicles.
The crews critiqued what worked and what failed, then planned the next day's assault. According to the MCVTHF, "After the evening meal, the next day's plan of attack was worked out for the team."
Col. Bob Thompson, commanding officer of 1/5, watched the armor crews return from combat each day.
"They reminded me of knights returning to the castle after fighting the dragon," Thompson said.
When asked what he would have done without the tanks and Ontos, Thompson was blunt: "Oh, we would have won; it would have taken us longer, and we would have sustained greater casualties, greater than the 60 percent we did."
Over the course of the battle, Ontos and Patton tanks proved vital to retaking the southern half of the city and helping the Marines and ARVN forces in capturing the Citadel.
While the Marines took Hue and suffered heavy casualties in doing so, the infantry were forever grateful for the ugly tank-hunter that struck fear into the hearts of every communist in the city.
The Cost
The armor crews paid a heavy price for their efforts in Hue. The Ontos' thin armor usually stopped small arms fire and grenade fragments but offered little protection against RPGs and B-40 rockets.
Cpl. Mario Tamez, a Patton tank commander who fought alongside Ontos crews in North Hue, estimated his platoon took more than 63 RPG and B-40 rocket hits during their 9 days inside the Citadel.
On Feb. 6, an Ontos moved forward to blast an entry into the Provincial Headquarters. A B-40 rocket disabled it before it could fire. The next day, another Ontos was knocked out while supporting 1st Battalion, 1st Marines. The driver was killed as the rest of the crew bailed out.
Ammunition was a constant problem. Each Ontos carried only 18 rounds. "Marines had to hold up their advance from time to time for lack of 90mm tank and 106mm Ontos ammunition," according to the MCVTHF.
Resupplying the vehicles through the contested streets was dangerous and slow. Loaders were usually targeted. At times, Marine Corps infantry were tasked with replacing the high losses suffered by Ontos crews.
By Feb. 25, the battle was over. The Marines had retaken Hue at the cost of over 200 Americans killed and more than 1,500 wounded. ARVN forces lost over 400 killed and over 1,000 wounded.
Estimates of NVA dead range from 5,000 to 8,000 total. Fifty percent of the city was in ruins, and most of the population was left homeless, with thousands dead, wounded, or missing.
The Thing’s Legacy
Marine Corps Warfighting Publication 3-35.3, the official doctrine for Military Operations on Urbanized Terrain, uses Hue as its primary case study. It outright states, "The Marines' most effective weapons during the battle were the M48A1 Patton tank and the M-50 Ontos."
Cheatham later called the Ontos "as big a help as any item of gear we had that was not organic to the battalion."
The Marine Corps finally withdrew the Ontos from service in 1969. The vehicle had never been used for its intended purpose. Designed to destroy Soviet tanks on European battlefields, it found its calling as an infantry support weapon in the streets of Hue.
While it proved its worth in Hue, Marine Corps doctrine and leaders did not anticipate fighting similar battles in the future. The Ontos had earned its place in Marine Corps history, but its brief service was done.
Of the 297 M50 vehicles produced, most were scrapped shortly after the war. A few vehicles now rest in museums around the world. The National Museum of the Marine Corps in Quantico, Virginia, has one on display, as does the National Military Vehicles Museum in Dubois, Wyoming.
In Nicholas Warr's "Phase Line Green," a firsthand account by a platoon commander with 1st Battalion, 5th Marines at Hue, Marine infantrymen greeted each Ontos salvo with cheers of "Get some!"
The M50 Ontos was short-lived and saw limited combat during its service. At Hue, it proved a formidable force-multiplier in the bloody urban combat. It remains one of the most unique vehicles the Marine Corps has ever fielded. For the Marines who fought in Hue and the NVA who faced it, the Ontos is an unforgettable beast.
