On the 2nd of January, 1963, 13 M113 armored carriers advanced into the rice paddies at Ap Bac in the Mekong Delta. The Viet Cong shot 14 of the 17 50 caliber gunners off the tops of those vehicles in minutes. The ARVN mechanized squadron withdrew in defeat. 7 years later, the 17th of March, 1970, American forces in Cambodia captured a directive from the PAVNB three front command. The order was explicit.
When engaging American armored columns, soldiers were to break away and avoid shooting back. Same vehicle, same aluminum hull, same 50 caliber Browning. But somewhere between 1963 and 1970, someone had changed what that vehicle was and what it could do to an ambush so completely that an entire enemy front command told its soldiers to run rather than fight it.
The M113 armored personnel carrier arrived in South Vietnam on the 30th of March, 1962. 32 vehicles were issued to two ARVN mechanized rifle companies. American doctrine was absolute. This was a battle taxi. Carry infantry under armor, dismount them at the tree line, then pull back. One weapon only, the M2 HB 50 caliber Browning machine gun on an open pintle mount at the commander’s cupola.
No shield, no side guns, nothing protecting the gunner above the waist. The Viet Cong studied captured American manuals and understood the arithmetic immediately. Kill the man standing up and the 12-ton box goes blind. On the 2nd of January, 1963, they proved it. Captain Ly Tong Ba’s fourth mechanized rifle squadron, 13 M113 vehicles, was ordered into the rice paddies near Ap Bac to relieve pinned infantry and downed helicopter crews.
What Ba drove into was 320 to 350 fighters of the 261st and 514th VC battalions dug into foxholes deep enough to stand in, tipped off by the legendary spy Pham Xuan An and by their own intercepts of unencrypted ARVN radios. The M113 vehicles bogged in the mud of the Cong Ba Ky canal. They came forward in single file.
The VC waited until 50 m, then shot the exposed 50 caliber gunners through the chest. Grenades sailed onto the open tops of the carriers. A flamethrower M113 sent forward to burn the tree line had been loaded with the wrong mixture of thickening agent and its 200-m jet died at 30 m. 14 of 17 gunners were killed or wounded in minutes.
Ba was knocked unconscious inside his own track. Lieutenant Colonel John Paul Vann told reporters the next day, “A miserable damn performance.” The VC had found their answer. Kill the man in the cupola and the track goes dumb. What happened next almost never appears in American histories because the fix was not American. Within weeks of Ap Bac, ARVN crews and the 80th Ordnance Unit started improvising.
Their first attempt was armor plate cut from the scrap hulls of sunken ships in the Saigon River. The plate was too soft and bullets went straight through. Their second try, salvaged armor from wrecked fighting vehicles, held. They welded gun shields around the 50 caliber cupola.
They added side pintle mounts for M60 machine guns. They bolted extra steel under the belly to protect against mines. By the end of 1964, every ARVN M113 in Vietnam had a gun shield. But the Vietnamese had done something bigger than add a piece of steel. They had inverted American doctrine. The M113 was no longer a taxi, it was the fight.
Captain Ba himself recorded that Viet Cong prisoners told him that they were very afraid and that they dared not fire at mechanized units, especially units painted in camouflage stripes. The US Army Material Command followed in July, 1964 and adopted the package pioneered by the ARVN as the standardized kit in 1965.
FMC factories in San Jose and on Okinawa stamped them out by the thousand. The name ACAV, armored cavalry assault vehicle, was coined by troopers of the 11th Armored Cavalry Regiment when they stepped off the boats at Vung Tau on the 7th of September, 1966. It was never an official designation. The Blackhorse Regiment had their kits installed stateside before shipping.
The name stuck to the hardware and the doctrine alike. Now multiply the firepower. A single ACAV carried a 50 caliber at 450 to 600 rounds per minute plus two M60s at 550 rounds per minute each for 1,500 to 1,900 rounds per minute from one vehicle. That was more automatic firepower than an entire US rifle squad.
Crews stripped out every seat but the driver’s and stacked ammunition wall to wall, two layers deep. A cavalry troop fielded roughly 17 ACAVs. A full squadron with its tank company and howitzer battery put 50 ACAVs and 17 and 48 A3 Pattons on a single road. 30 to 60 machine guns firing at once before you counted the Patton’s 90 mm main guns.
The question was what to do when the ambush came. The answer was a piece of battle drill so simple it could be shouted over a radio in 3 seconds. When a column was hit, the lead vehicle kept facing forward, the trail vehicle covered the rear, and every vehicle between pivoted 45°. Odd-numbered vehicles to the left, even-numbered vehicles to the right, rolling off the road into a zigzag.
The road stayed open as a spine for ammunition and medevac. The 50 calibers raked outward from 50 m. The M60s opened at 25 m. It refused to stop in the kill zone. It replaced the shock of the ambush with a saturating counter volley and it turned a linear column into a starfish of interlocking fire. On the 26th of March, 1970, deep in War Zone C, a 90-man infantry company called Racer 2-9 was surrounded by 400 NVA in a horseshoe bunker complex.
4 km away, a cavalry captain heard the distress call. That story is coming. But first, the proof that the herringbone worked. Suoi Cat, the 2nd of December, 1966. Lieutenant William Radosevich’s small convoy from First Squadron, 11th ACR, consisted of two M48s, three ACAVs, and two trucks. They drove into a prepared ambush on Highway 1 by a reinforced battalion of the 275th VC Regiment.
Radosevich’s lead tank hit a command detonated mine triggered 10 m early. Wounded, he screamed the herringbone order over the radio. Within minutes, the geometry reversed. Captain John Landry’s B Troop relief force herringboned its way into the fight. Company D launched 7 minutes after first contact. Artillery and AC-47 Spooky gunships sealed escape routes through the night.
The sound was more than 30 machine guns opening simultaneously, brass raining onto aluminum decks, the M2’s slow percussive thump at half the cyclic rate of the flanking M60s beside it. At least 99 VC dead. American losses, one killed and 22 wounded. The 275th’s offensive capability was broken for months.
Colonel Don Starry wrote that the herringbone had allowed commanders to fix and hold an entire ambushing force. The ambush, the Viet Cong’s most practiced tactic, had been inverted into a trap for the ambushers. Now the debt comes due. Charlie Company, Second Battalion, Eighth Cavalry, First Cavalry Division, roughly 90 men, call sign Racer 2-9, was surrounded by an estimated 400 NVA in triple canopy jungle near the Cambodian border.
4 km away, Captain John B. Poindexter’s Alpha Troop, First Squadron, 11th Armored Cavalry Regiment with nine Sheridans, 15 ACAVs, three mortar carriers, and roughly 200 troopers, heard the distress call and volunteered without orders. Saddle up and move out. When a fellow commander protested, Poindexter’s answer was flat.
“That’s not what the 11th Cavalry does.” Alpha Troop bulldozed 2 and 1/2 miles of bamboo and undergrowth at a pace slower than a man can walk. Machine gun barrels ran white hot. A driver the men called Huge dismounted under fire to change a glowing barrel with a dry towel wrapped around his hand. He said, “You are supposed to have an asbestos glove, but in the middle of battle, you do not have a glove.
” Inside the perimeter, Private Paul Evans, an 18-year-old, was convinced he was about to die. Then United States armor thundered out of the jungle. Alpha Troop broke the siege. At least two were killed and 20 were wounded. The action received no recognition for 39 years. Poindexter spent decades tracking down his men.
On the 20th of October, 2009, President Barack Obama presented the Presidential Unit Citation to 119 Alpha Troop veterans in the White House Rose Garden. He said to the troopers, “You are not anonymous anymore.” The Viet Cong called the M113 the Rong Xan, the green dragon. By 1965, US forces had captured a full VC training manual titled Attack on M113 APC, listing characteristics, organizations, weak points, and counter tactics.
It was the product of a learning army. They learned fast. 57-mm recoilless heat rounds appeared by the summer of 1963. RPG-2 arrived by 1965, a shaped charge that cut aluminum like butter. RPG-7 arrived by 1966 with enough penetration to ignite the hull itself. >> [music] >> Engagement ranges pushed back from 20 m at Ap Bac to 70, then 100, with recoilless rifles used like a sniper weapon rather than a close-in ambush tool.
But the decisive answer was already in the ground, mines. Between November 1967 and March 1970, 1,342 M113s were destroyed by land mines alone. 73% of all vehicle losses, more than RPGs and recoilless rifles combined. The M113’s flat aluminum belly was its original sin. Command detonation mines built from unexploded 155 mm artillery shells could destroy a 12-ton vehicle and kill everyone inside.
Crews welded steel plates underneath, then titanium slabs, then doubled and tripled sandbags across the floor. And then by 1968 and 1969, they simply stopped riding inside. They rode on top behind sandbag castles because the uncertain fate inside was worse than the certain exposure above. The ACAV, born from the open cupola vulnerability of App back, had returned its crews to total exposure to survive the enemy’s evolution.
Bob Kickinwhites of the 11th ACR, after the second ambush at Soy Cat on the 21st of May, 1967, which killed 16 Black Horse troopers in a single afternoon, later recalled that he was so scared and the adrenaline was pumping so hard that afterward he felt very cold. So cold in fact that his teeth started to chatter and he felt like he was going to freeze to death.
Roughly 80,000 M113 family vehicles were built, one of the most produced armored fighting vehicles in history, still serving with more than 40 nations. Hundreds have been sent to Ukraine since 2022. [music] The M2 Bradley’s core requirement was to fight from the vehicle, not merely to the vehicle.
That requirement was written by ACAV veterans led by Don Starry at Fort Knox. The Bradley exists because the Green Dragon proved that mechanized infantry and the machine had to be one thing. The men who rode them named their tracks the way bomber crews named their aircraft. Aztec Warrior, Virgin Eater, Snoopy, The Nympho. Ron Holland of the 11th ACR remembered First Sergeant Willie Johnson, who was killed by an RPG near the Cambodian border on the 5th of March, 1970.
Ron said that Willie was a career soldier, their first sergeant, a leader, advisor, confessor, and friend. He said he never called him Willie, but always called him Top. The Army never told Willie’s family how he died. The B3 front order was simple. Break away, avoid shooting back, conserve forces. The Green Dragon won the tactical argument.
It made itself too expensive to ambush. The enemy’s answer was to stop ambushing. They mined the road instead. They let the Americans drive where they pleased and blew the flat aluminum bellies up from below. So the crews sat on the roof in the heat watching for wires in the dirt, knowing that every meter of road might be the one. Find the bastards, then pile on.
That was Patton’s order. The ACAV was built to do exactly that. What nobody told the crews was what came after the piling on was finished, the long ride home on top in the sun, listening for the click that meant the road had learned to fight back.
