Hue City, early February 1968. Delta Company, 1st Battalion, 5th Marines is pinned from three directions in a narrow street south of the Perfume River. Cannot advance. NVA fighters are dug into a concrete building at the end of the block >>  >> firing from every window. Cannot flank. The alleys are kill zones.

 Cannot  retreat. The ground behind them is already zeroed. Every option is a bad one. Then the grinding of light tracks on broken masonry. A squat steel box.  9 tons bristling with six enormous tubes rolls through the rubble and stops. The commander traverses a single .50  caliber spotting rifle toward the window where most of the fire is concentrated.

Fires one round. One tracer. One puff of white smoke against the window frame. The NVA abandon the building. Every fighter inside scatters. The main guns never fire. One marking round empties a fortress. The Marines called it the thing. October 1948. Fort Monroe, Virginia. A conference room full of US Army officers staring at maps of Central Europe.

Gaming out the nightmare that kept NATO planners awake. Soviet armor flooding through the Fulda Gap. Thousands of tanks pouring across the North German plain faster than NATO could reinforce. The requirement they drafted that day was specific. A small air transportable anti-tank vehicle. Something light enough to fly into a crisis on a cargo plane.

 Something that could kill a T-34 and disappear before the next wave arrived. That was the war they designed for. A war of open plains, massed armor, and clear fields of fire across European farmland. 17 years later, the weapon they built for that war rolled off a landing craft into Vietnam. Where there were no Soviet tanks, >>  >> no open plains, and no fields of fire longer than the distance  between two buildings.

 On a narrow street in an ancient Vietnamese city. What the Marines had instead was the M50 Patton. 50 tons. A 90 mm gun that could destroy anything it hit. And a footprint so heavy it couldn’t cross the pontoon bridges that connected half the operational area in I Corps. In Hue’s narrow alleys, some barely wider than the tank itself, the Patton couldn’t turn, couldn’t maneuver, couldn’t reach the buildings where NVA fighters were dug in behind reinforced concrete walls.

Infantry weapons couldn’t breach those walls. Artillery couldn’t distinguish one building from the next in an urban maze where the enemy was sometimes one floor above the Marines trying  to kill them. Close air support risked leveling the very positions the Marines needed to occupy. The gap was specific and lethal.

 No weapon in the Marine inventory could deliver precision direct fire against a fortified concrete building in a space too narrow for a tank. Spring 1966 near Da Nang. A column of Ontos vehicles from the 3rd Anti-Tank Battalion moves through the VM Dong Crossing. PFC Greg Weaver is riding as acting commander of his vehicle.

 The position directly above the ammunition storage  rack beneath the floor. His Ontos strikes a buried mine. The blast doesn’t just damage the vehicle. It detonates a 106 mm round stored directly underneath Weaver’s position. The turret, all six rifles, the steel turntable, everything above the hull blows clean off the vehicle.

Weaver dies almost immediately. His platoon commander Alan Hoof watches the whole thing from the vehicle behind. Years later, Weaver’s brother Ben confirmed the details in correspondence with historian Peter Brush. 6.4 mm, 1/4 of an inch. That was the thickness of the Ontos floor armor.

 The only thing between Greg Weaver and a buried mine in a war where buried mines were the single most common killer of armored vehicles. The gap wasn’t just that the Marines lacked a weapon to breach buildings. It was that the tools they did have were killing their own crews in ways the designers sitting in Indiana in 1950 had never imagined.

 And nobody in the Marine Corps was thinking about how to fix it. Major D.C. Satcher writing in Marine Corps Gazette in November 1969 under the title Ugly Ontos is underrated identified the blind spot with precision. The Ontos never appeared in tactics problems at the basic school. There was no Ontos specific military occupational specialty.

 An officer might serve one tour commanding an Ontos platoon. Learn its capabilities through hard experience. Rotate home. And whatever he’d learned never entered institutional memory. The weapon existed in a doctrinal vacuum. No one was trained to employ it. No one planned operations around it. No one imagined what it could become.

 So how did a vehicle the Army had rejected the Marines had accepted out of desperation and the training establishment had ignored. How did it become what Colonel  Stanley S. Hughes commanding the 1st Marines at Hue called the most effective of all Marine supporting arms? The answer starts in a tractor  factory in Indiana.

November 1950. LaPorte, Indiana.  The Allis-Chalmers Manufacturing Company with known primarily for building farm machinery  walls off a section of its facility under confidential classification. And assigns a team of up to 50 engineers to a project that has  nothing to do with tractors. Their task.

 Design the strangest  armored vehicle in the American inventory. The official designation was a masterpiece of military nomenclature. Rifle multiple 106 mm self-propelled M50. The name that stuck was applied in September 1951. Ontos. Greek for thing. The vehicle was so singularly odd-looking. A squat steel box bristling with six enormous rifle tubes arranged in triangular clusters. Three per side.

That reportedly no one on the program dared name it after a famous general. For fear the general’s family might take offense. So they called it what it was. A thing. The thing. The concept behind the thing was simple and radical. Mount six M4 0106 mm recoilless rifles on a chassis light enough to be carried inside a C-119 Flying Boxcar or a C-130 Hercules.

 Fly it to the  crisis point. Fire a devastating salvo on enemy tanks. Reverse. Reload. Disappear before return fire arrives. Shoot and scoot. The entire tactical doctrine compressed into three words.  Development ran through multiple prototypes. The T164 carried four rifles. The T165 completed in 1952.

Mounted all six on M56 Scorpion running gear. But with only 15° of turret traverse. The gunner practically had to aim the entire vehicle. The improved T165E2 designated in January 1955 widened traverse to 40° and became the basis for the production model. Testing began at Aberdeen Proving Ground in March 1954.

The moment all six rifles fired simultaneously defined the Ontos as completely as any specification sheet ever could. The backblast, the jet of superheated gas that recoilless rifles vent rearward to eliminate recoil, knocked bricks out of nearby buildings and shattered car windows in the parking lot. The engineers at Aberdeen now understood what they had built.

 So did the Army officers watching. They hated it. When the prototype was formally presented in 1953, Army evaluators cataloged its sins with bureaucratic thoroughness. Too small. Too tall relative to its width. Too cramped for the three-man crew. A commander gunner, a driver, and a loader who would have to operate inside an interior so tight that crews would later drive with the rear doors permanently open just to function.

Ammunition storage was pathetic. 18 rounds total. Six loaded in the rifles, eight in a rack beneath the floor, four stowed inside the right rear compartment. The armor was 13 mm of welded rolled homogeneous steel. Half an inch on every  face. A quarter inch on the floor. Enough to stop small arms fire.

Enough to stop grenade fragments. Not enough to stop anything with the word  anti-tank in its designation. But the killing flaw, the one that made every officer in the room shake his head, >>  >> was reloading. All six rifles had to be loaded from outside the vehicle. After firing a salvo, the loader had to exit through the rear doors into whatever was happening outside, manhandle 38-lb rounds into breaches mounted 7 ft off the ground, and hope the enemy was a poor shot.

In 1955, the Army formally declared the M50 Ontos >>  >> unsuitable for use by field forces. That should have been the end. But, historian William F. Floyd, Jr., later identified what was really happening behind the rejection. General J. Lawton Collins,  Army Chief of Staff, feared the Ontos program would siphon procurement dollars away from additional tanks.

  The Ontos didn’t fit the Army’s offensive fighting doctrine. It was a defensive ambush weapon in an institution that prized the armored charge. The Ontos wasn’t killed by its engineering flaws. It was killed by bureaucratic politics. The deficiencies were real. The rejection was institutional. The Marine Corps saw the same vehicle and reached a different conclusion.

November 1954,  the USMC formally replaced the Army as program lead. >>  >> The Marines were desperate for any anti-tank capability. They were pragmatic about tradeoffs, >>  >> and they were profoundly unimpressed by the Army’s objections about crew vulnerability. One assessment captured the Marine position with a brevity that borders on comedy. Being shot at was nothing new.

On August 12th, 1955, Allis-Chalmers received a production contract for 297 vehicles, down from the original plan of 1,000. The first vehicle was accepted on October 31st, 1956. Between 1963 and 1965, 176 were upgraded to the M50A1 variant, swapping the original General Motors 302 engine, 145 horsepower, for a Chrysler 58, producing 180.

The upgrade also dropped ground pressure to 4.7 lb per square inch. That number would matter more than anyone knew. What the Marines now possessed was a 9-ton contradiction. Ferocious armament, six rifles capable of destroying any tank on Earth, breaching any concrete wall, or launching 57,600 steel flechettes in a single salvo, bolted onto a chassis with the protective capacity of a filing cabinet.

 Too much gun, not enough armor, too little ammunition. No doctrinal home, no training pipeline, >>  >> no institutional champion. It was, by every conventional measure, a failure. The Marines took it to Vietnam anyway. Section four, combat proving. The first engagements. March 8th, 1965, Da Nang. The Ninth Marine Expeditionary Brigade hits the beach, and with them comes the Ontos.

M50A1 C33, Company C, third platoon, third vehicle, rolls off a landing craft onto Red Beach 2, photographed in the act, one of the first tracked vehicles of the American ground war in Vietnam. Within a year, both the first and third anti-tank battalions are ashore. Each battalion fields three anti-tank companies, three platoons of five Ontos per company, 45 vehicles per battalion, 15 allocated to each infantry regiment in a Marine division.

The organization chart was ready. The enemy was not. There were no Soviet  tanks, no Chinese armor, no armored threat of any kind. The weapon the Marines had accepted specifically to kill tanks had arrived in a war where the enemy didn’t have any. What happened next was not planned. It was improvised by officers and crews  who had no doctrine, no training syllabus, and no institutional guidance on what to do with six recoilless rifles mounted on a vehicle  the size of a large car.

August 18th, 1965, south of Chu Lai, Operation Starlight, the first major United States ground offensive of the Vietnam War. A platoon of four Ontos from the third anti-tank battalion lands with Company K, third battalion, third Marines in the amphibious assault wave. At 07:30, tanks and Ontos roll off landing craft utility vessels and push inland.

Backed by two Ontos, K Company drives into the village of An Quang and secures the high ground beyond. In one engagement, an Ontos crew chief finds himself unable to fire his 106-mm rifles. Marines are positioned directly behind the vehicle, inside the backblast zone, where the jet of superheated exhaust gas would kill them as surely as enemy fire.

His vehicle-mounted machine gun jams. So, he does what Marines do when the plan fails. He grabs the .50 caliber spotting rifle, a secondary weapon designed for nothing more than marking targets, and opens fire on the enemy with it. Improvisation under fire. The Ontos DNA emerging for the first time in combat.

Operation Starlight killed 614 Viet Cong against 45 Marines dead. The Ontos had drawn blood, but it hadn’t yet found its true role. That changed 10 months later on a pontoon bridge. June 29th, 1966, Route 1, Operation Jay. A Viet Cong force ambushes a South Vietnamese convoy, and the nearest Marine reaction force includes both M48 Patton  tanks and Ontos from B Company, third anti-tank battalion.

Between the Marines and the fight is a river spanned by a single pontoon bridge. The Patton’s weigh 50 tons. The bridge will not hold them. The tanks stop at the riverbank, their 90-mm guns useless on the wrong side of the water. The Ontos weigh nine. B Company’s vehicles cross the bridge at  speed, the only tracked armor that can reach the battle.

As the VC break contact and cross open ground, an Ontos platoon catches a VC  squad silhouetted on a ridgeline and fires a single 106-mm salvo. The squad ceases  to exist. Over 185 enemy killed by the end of the operation. This was the pivot. The Ontos’  defining weakness as an anti-tank weapon, its featherweight chassis,  the light armor that couldn’t survive a direct confrontation with anything serious, had just become its decisive advantage.

 It went where the Patton could not follow. Ground pressure of 4.7 lb per square inch meant the Ontos could cross flooded rice paddies, navigate pontoon bridges, and traverse soft ground that would swallow a 50-ton tank to its hull. The flaw was the feature. The failure was the strength. And then, the Marines discovered the beehive round, the flechette anti-personnel round designated beehive for the distinctive buzzing sound the darts made in flight, contained approximately 9,600 2-in winged steel flechettes per shell.

Fin-stabilized darts packed into a canister that burst open after firing and spread in a lethal cone. One round, 9,600 darts. Six  tubes loaded with beehive. 57,600 flechettes in a single salvo. The Ontos became six enormous shotguns on tracks. The fire control system that aimed all of it was elegant in its simplicity.

Four of the six rifles carried M8C .50 caliber spotting rifles, secondary weapons that fired  tracer rounds ballistically matched to the 106-mm trajectory out to 1,100 yd. The gunner aimed through his periscopic sight, fired the spotting rifle, watched for the white smoke puff where the tracer struck, and then fired the main gun along the identical path.

  As one Marine instructor put it, the system was simple enough for the average Marine to master as easily as he has the pinball machine in the local drugstore. Combined with heat rounds that punched through any concrete wall, and HEP plastic explosive rounds that pancaked against masonry before detonating, blasting 4-m holes through building walls at 300 to 500 yd, the Ontos now offered a direct fire menu that no other Marine weapon system could match.

Anti-armor, anti-personnel, anti-structure, all from a vehicle that weighed less than a loaded dump truck. September 10th, 1967, Con Thien. The third battalion, 26 Marines,  is dug in along the DMZ when the entire 812th NVA regiment attacks. Lance Corporal Randall A. Browning, an Ontos commander with a company third anti-tank battalion, takes serious wounds early in the assault but stays in his vehicle and keeps fighting.

As waves of NVA infantry charge the Marine perimeter, Browning repulses them with every weapon available. The 106 mm rifles, >>  >> the spotting guns, anything that fires. Fellow veteran Rick Streck,  who was there that day, said it plainly. His small tank Ontos was very important  in saving an entire battalion of 26 Marines.

Canister fire from the Ontos mowed rows of NVA soldiers down like they were corn. Streck’s >>  >> not embellishment. Browning was nominated for the Medal of Honor. He received the Navy Cross instead.  Between Con Thien and the coming storm, one more story belongs here. Told briefly because brevity is what the man himself would have wanted.

First Lieutenant Philip H. Sauer, platoon commander, second platoon A company, third anti-tank battalion, had led the first Ontos sent to Khe San via the first Rough Rider convoy on Route 9 in March 1967. On April 24th, ambushed by more than 30 NVA troops on Hill 861, Sauer drew  his .45 pistol, provided covering fire, and ordered his men off the hill.

They made it. He did not. His posthumous Silver Star was not awarded  until 51 years later in a 2018 ceremony at Camp Pendleton. Major General Eric M. Smith said at the ceremony, “That’s what Marines do. Senior Marines taking care of junior Marines.” >>  >> The Ontos had proved it could cross bridges tanks couldn’t cross, kill infantry in the open, break bunkers, and save battalions.

But its defining task was still ahead. 26 days of the most intense urban combat American forces had experienced since the Second World War. January 31st, 1968. The Tet Offensive. North Vietnamese forces infiltrate and seize most of Hue, South Vietnam’s ancient imperial capital, a city of palaces  and narrow streets bisected by the Perfume River with the massive walled citadel on the north bank, and the modern new city on the south.

What follows will take 26 days to resolve. The first and second Ontos platoons of A company, third anti-tank battalion, approximately 10 vehicles, deployed to Hue under the overall armor command of Captain Conwell W. Casey, commanding A company, First Tank Battalion. They work alongside M48A3 Patton tanks from C company, First Tank Battalion.

The partnership that emerges is symbiotic. The 9-ton Ontos navigates the cramped alleys and crosses the narrow bridges where 50-ton Pattons cannot physically fit. The Pattons provide the heavy armor and sustained firepower the Ontos lacks. Neither is sufficient alone. Together they become the most effective direct fire combination in the battle.

February 1st. Two Ontos accompany Captain Ron Christmas’s Company H, Second Battalion, Fifth Marines in a convoy across the An Cu Bridge into Hue, and take fire the moment they cross. The urban warfare that follows has no precedent in the Marine Corps Vietnam experience. NVA regulars are dug into concrete buildings, firing from every window, every rooftop, every doorway.

 The streets are kill zones. Moving down them means dying. Lieutenant Colonel Ernest C. Cheatham Jr., commanding 2/5 Marines, solves the problem with the Ontos at its center. The technique he develops becomes the template for the entire battle. The Ontos or tank commander reconnoiters a target building alongside infantry, identifies the wall to breach.

The vehicle then advances at full speed toward the building while infantry lays down covering fire from behind. The commander halts, fires two to three rounds directly into the structure. The effect is immediate and absolute. A 4-square-meter hole punched through the wall or the entire exterior face demolished.

The vehicle reverses at full speed to friendly lines. Infantry pours through the breach into the building rather than advancing down the NVA-covered street outside. Cheatham doesn’t just command this technique from a command post. He walks forward under fire personally to ground guide an Ontos to the Perfume River bank, pointing at a specific spot on the citadel wall on the far shore that’s hitting his Marines with flanking fire. Two spotter rounds.

The white smoke puffs bloom against ancient masonry. Then ripple fire from a pair of 106s. A large chunk of the citadel wall collapses into the moat. Harassing fire from that direction ceases permanently. Cheatham called the Ontos as big a help as any item of gear we had that was not organic to the battalion.

Then came the moment that defined the thing forever. Delta Company, First Battalion, Fifth Marines pinned, cannot advance, cannot flank, cannot retreat. Going back means crossing ground the NVA already have zeroed. The company is stuck, taking fire from a fortified building, and every option is a bad one. An Ontos rolls forward through the rubble, >>  >> stops.

The commander aims the .50 caliber spotting rifle at a window where most of the incoming fire is concentrated. Fires one round, a single tracer, a single puff of white smoke blooming against the window frame. The NVA abandon the building. Every fighter inside scatters. The Ontos never fires its main guns. One spotting round, a marking round, a weapon designed to do nothing but show where the real shot will land, empties a fortified position.

Captain Dale Dye, combat correspondent, witnessed it. His assessment carries the weight of a man who had watched the Ontos work for weeks. Apparently, the word had spread from NVA survivors of the south side fighting to their buddies on the north side. When the thing rolls up on your position, it’s time to un-ass the area.

The weapon’s reputation had become the weapon. The ingenuity didn’t stop there. A lance corporal, unnamed in the record, which means he never received proper credit, approached Captain Ron Christmas with an idea that sounded like lunacy. Mount a 106 mm recoilless rifle on an M274 mechanical mule, a glorified motorized platform barely larger than a go-kart, drive it through a hotel lobby to the far side, and fire it down a street.

The massive backblast would fill the lobby with smoke and debris, creating an improvised smoke  screen to conceal an entire infantry company crossing the open street behind it. Christmas endorsed  the plan immediately. It worked. When white phosphorus smoke  rounds ran out, Marines discovered that beehive rounds fired into masonry walls created their own dust clouds  thick enough to screen movement.

They were inventing urban warfare  doctrine in real Corporal Charles McMahon came upon a stalled convoy in Hue’s streets. Two Ontos vehicles sitting there, undamaged, their 106 mm tubes empty. The crews were dead. An order prohibiting travel with loaded rounds had forced the crews to climb outside to reload when the ambush hit.

Exposed, fumbling with 38-pound shells while rounds snapped past them, they never made it back inside their vehicles. Three Ontos were knocked out during the entire battle. This was the cruelest loss, not to enemy firepower, but to a regulation that turned the Ontos’ worst design flaw into a death sentence. Major Robert H.

 Thompson, commanding First Battalion, Fifth Marines, was asked after the battle what he would have done without tanks and Ontos. >>  >> His answer landed like a body blow. “Oh, we would have won. It would have taken us longer, and we would have sustained greater casualties,  greater than the 60% we did. Greater than 60%.

And that was with the Ontos.” The battle for Hue ended on March 2nd, 1968. The Marine Corps’ official MOUT doctrine, military operations on urbanized terrain, subsequently cited Hue as its primary case study, and stated in plain language what every Marine who fought there already knew. The Marines’ most effective weapons during the battle were the M48A1 Patton tank and the M50 Ontos.

13 mm of welded rolled homogeneous steel. Half an inch on every face, a quarter inch on the floor. The Ontos stopped rifle bullets and grenade fragments and nothing else. RPGs punched through it. Mines tore it apart from below. Recoilless rifle rounds, the same type of weapon it carried, penetrated its armor with ease.

The paper-thin floor was a death sentence over buried ordnance. And buried ordnance was Vietnam’s  most prolific killer of armored vehicles. PFC Greg Weaver learned this at the VM Dong Crossing. The mine, the stored round detonating beneath him. The turret blown clean off the hull. A quarter inch of steel between a Marine and the thing that killed him.

Then there was the reloading. 18 rounds total, six in the rifles, 12 stowed inside. Each one loaded from outside the vehicle. The loader fully exposed from the waist up while wrestling 38-lb shells into breeches 7 ft off the ground. Captain Dale Dye understood the arithmetic with a dark clarity that only someone who’d watched it happen could articulate.

>>  >> The Ontos went bang with a six-barreled vengeance. And that was an attractive feature for Marines who had enough suicidal PFCs  to sustain the vehicle’s three-man crews. Dye described one of those PFCs in action at Hue. A skinny kid from Kansas who bolted out of his cubbyhole in the back of the vehicle every time the rifles went dry, ignoring incoming rounds pinging off the armor around him, calmly reloading one tube after another.

“He was grinning the whole time,” Dye wrote, “like some carny running the grift on rubes at a low-rent county fair shooting gallery.” That grin is the Ontos in a single image. Courage and absurdity and mortal vulnerability. All in the same frame. The NVA adapted. They targeted the thin armor with B-40 rockets, the RPG variant that could kill the Ontos from any angle at any range within its effective envelope.

Three Ontos destroyed at Hue. The convoy ambush that caught crews outside reloading. Somewhere in the wreckage of the Tet Offensive, a photograph was taken of Viet Cong troops  examining an abandoned M50A1. Studying it, learning its joints and seams, figuring out where to hit it next time. And the institution that should have been learning alongside the enemy was instead dismantling the weapon’s organizational home.

>>  >> The 1st and 3rd anti-tank battalions were decommissioned in December 1967, 1 month before the Tet Offensive proved the Ontos was the most effective direct fire support weapon the Marines possessed.  No Ontos-specific MOS. No training pipeline. No doctrinal manual. Officers who learned its capabilities through blood and improvisation rotated home and what they knew rotated with them.

The vehicle was never replaced by an equivalent system. The anti-armor mission shifted to TOW guided missiles and eventually the LAV-AT. The institutional memory died with the units. The Marines decommissioned the weapon while it was winning. Simultaneous with Hue and largely forgotten beneath its shadow, 10 M50A1 Ontos sat on the defensive perimeter of Khe Sanh Combat Base where Colonel David E.

 Lownds’ 26 Marines faced an estimated 20,000 to 30,000 NVA troops during a 77-day siege. The Ontos were loaded exclusively with beehive rounds and positioned as a mobile reserve ready to concentrate at any threatened sector. Author Robert P. Sorley in his history, The End of the Line, wrote that the Ontos at Khe Sanh had enough flechette ammunition to pin the entire North Vietnamese Army to the face of Co Roc Mountain.

A single six-gun salvo would have launched 57,600 steel darts into the teeth of any human wave assault. The total recoilless rifle count along the perimeter reached 92 single or Ontos-mounted 106-mm weapons, a density of direct fire that would have turned any ground attack into a slaughter. The ground attack never came.

 The feared human wave assault never materialized. The Ontos’ greatest contribution at Khe Sanh may have been purely psychological, deterrence so convincing that the weapon won by never firing. A battle decided by reputation alone. By May 1969, the Marines deactivated all remaining Ontos units. Some worn-out hulls were handed to the US Army’s Company D, 16th Armor, attached to the 173rd Airborne Brigade, which operated them until the part supply dried up entirely.

After that, the stripped hulls were filled with sandbags and used as fixed bunkers.  The final indignity for a weapon that had been designed to kill Soviet tanks  at speed. The last operational M50 Ontos anywhere in the world served at Guantanamo Bay, Cuba until April 1980. Of 297 built, approximately 14 survive today.

The restored M50A1 at the National Museum of the Marine Corps in Quantico, Virginia sits in a diorama depicting the Tet Offensive, frozen in the moment it mattered most. At Camp Pendleton, another M50A1, one that actually fought at Hue, was restored by a civilian named Jerry Cook. The Ropkey Armor Museum in Crawfordsville, Indiana holds the original T165 prototype, the grandfather of every Ontos that ever rolled into combat.

Former Marine and collector Mike Scudder, who owns several vehicles, has put the rarity in perspective. There are more surviving World War I tanks than Ontos. The Ontos principle, massive recoilless rifle firepower mounted on a light expendable vehicle, did not die with the M50. It proliferated. Across Syria, Libya, and Yemen, technical vehicles mounting M40 106-mm recoilless rifles have become standard weapons of asymmetric warfare.

The Carl Gustaf 84-mm recoilless rifle has experienced a resurgence with American special operations forces in Afghanistan and Iraq. The Small Arms Survey documented what it called a resurgence of recoilless weapons globally, affordable, effective, portable, and devastating in the urban and irregular warfare environments that now define most armed conflict on Earth.

The Ontos was 50 years ahead of a doctrine the world hadn’t written yet. Brendan McNally of the Defense Media Network wrote the epitaph. Except for some Marine Vietnam veterans, the Ontos is today almost wholly unremembered. Unremembered. A vehicle that cleared the streets of Hue, that deterred a ground assault at Khe Sanh, that a single spotting round from its .

50 caliber could empty a fortified building without the main guns ever firing. Unremembered, returned to that street. Hue City. Early February 1968. Delta Company, 1st Battalion, 5th Marines. Pinned from three directions. No way forward, no way sideways, no way back. Then the grinding of light tracks on broken masonry. A squat steel box, 9 tons bristling with six enormous tubes.

The thing. It rolls to a stop. The commander traverses the spotting rifle toward a window where muzzle flashes are still winking. Fires one round, a .50 caliber tracer.  A puff of white smoke against the window frame. The NVA run, every one of them. The 106-mm rifle stay  silent. The building empties.

 One tracer, one puff of smoke. The reputation does the rest. Designed to kill Soviet tanks on the plains of Central Europe.  It never fought one. Built by a tractor company in Indiana, rejected by the Army, picked up by Marines who figured being shot at was nothing new. Fielded without doctrine, without training, without an institutional champion.

It carried 18 rounds and armor that wouldn’t stop a heavy machine gun. Its crew had to climb outside to reload. It became, in the words of the colonel who commanded Marines at the bloodiest urban battle of the Vietnam War, “the most effective of all Marine supporting arms.” Only 14 survive. The world has mostly forgotten the thing.

The men who fought beside it and the men who learned to run when it appeared never will.