April 1st, 1970. Fire support base Illingworth, 5 miles from the Cambodian border. A 219yard perimeter consisting of a lowearn burm and a ring of green plastic cases stamped with three raised words, front toward enemy. No concertina, no barbed wire. At 2:18 in the morning, the 272nd Main Force Regiment of the 9inth People’s Army Division opened with mortars, rockets, and recoilless rifles.
20 minutes later, nearly 400 soldiers came in behind the fire and rushed the wire that was not there. What stopped them was a weapon that weighed 3 12 lb, contained 1 and 12 lb of plastic explosive, and fired 700 steel balls in a 60° arc at 4,000 ft per second. The men inside the perimeter called it a clacker job.
The men outside the perimeter in the captured directives that came back from Hanoi were told it was a weapon to be neutralized by hand in the dark without sound. The weapon came out of the Korean War. American infantry on the line in 1951 had watched what happened when Chinese regiments came over hills in waves. A rifle could not stop a wave.
A machine gun could until it ran out of ammunition or men. The artillery solved the problem at a thousand yard, but not at 50. Inside 50 yards there was a gap and the gap was where infantry died. Two scientists working separately during the Second World War had pointed at the answer.
Yseph Meny in Hungary and Hubert Chardan in Germany had each found that when a sheet of explosive went off in contact with a heavy backing, the blast did not radiate. It went forward in one direction with a force that could be aimed. In 1952, an inventor named Norman Mloud began drawing what would become the directional anti-personnel mine.
His first design, the T48, was accepted by the United States Army at Picatney Arsenal as the M18 Claymore in 1956. Approximately 10,000 were produced. They were heavy, awkward, and not particularly lethal beyond 90 ft. The model that mattered came later. In 1954, Picatney issued a request for a better version.
A team at Aerogjet led successively by Guy Throner, Don Kennedy, Dr. John Bledsoe, and William Kinchelo spent 3 years rebuilding the weapon around four requirements. The mine had to weigh less than 3 12 lb. It had to strike a man-sized target at 50 m with 100% probability. Its fragment cone had to be no more than 8 ft high and 60° wide.
Its projectiles had to deliver at least 58 ft-lb of kinetic energy on impact, the threshold for a lethal injury. What they built was the M18A1. The Army type standardized it in 1960. The weapon arrived in Vietnam in the early summer of 1966. The M18A1 was 8 1/2 in long, 4 1/2 in high, and 1 and 1/2 in wide. Its plastic case curved slightly outward on one side and inward on the other.
Inside, behind a pound and a half of C4 explosive, sat 700 steel balls, each 1/8 of an inch across, set in epoxy resin. On the front, raised so a man could read them by touch in the dark, were the words front toward enemy. On the back, back. Two pairs of folding scissor legs underneath drove into soft ground. A peep site on top let the operator aim the cone.
The detonator was an M57 firing device, a green plastic squeeze handle that snapped when compressed. Soldiers called it the clacker. 100 ft of wire connected it to the blasting cap in the mine. The whole package, including mine, clacker, wire, and an instruction sheet sewn into the flap, came in a canvas bandelier called the M7 and weighed about 4 lb.
When the clacker was squeezed, the C4 detonated. The epoxy matrix shattered. The 700 steel balls launched forward at nearly 4,000 f feet per second, deformed by the blast into shapes resembling 22 rimfire rounds. At 50 m, the cone was 50 m wide and 7 ft high. Inside that cone, the hit probability on a standing man was 30%.
Out to 100 m, 10%. Fragments traveled as far as 250 m. The army paid about $119 per unit. The weapon did the work of a machine gun crew for the first half second of a human wave assault. By 1967, the claymore was carried by every American infantry company in Vietnam and their Australian, New Zealand, and South Korean allies.
Royal Australian Regiment patrols set them around fire support base PAT. South Vietnamese Popular Force militia were instructed in their use by Marine corporals. Long range patrols carried them on every mission. The claymore did two jobs. On the perimeter, it sat in front of a foxhole or bunker pointed outward.
The wire run back to the man inside. At night, when the fence and the trip flares and the listening posts had all failed, the claymore was the last thing between the enemy and the gunpit. On patrol, it was the trigger of the ambush, the device that put a wall of steel across a trail before the rifles opened up.
It closed a gap the army had carried since Korea. A hand grenade reached as far as a man could throw one with a killing radius of about 20 ft. A mortar started at 100 m minimum, often more. Between those distances, the infantry had only their rifles. The claymore filled the gap with a weapon that one man could carry, position in the dark, and fire by squeezing his hand.
In November 1965, elements of the first cavalry division dropped onto landing zone X-ray in the Idrang Valley. Lieutenant Colonel Harold Moore’s First Battalion, Seventh Cavalry, had taken the brunt of the first People’s Army assault. When Second Battalion, Fifth Cavalry, reinforced the position on the second day, the men ran fields of fire in front of the existing foxholes and set claymores out into the elephant grass.
A veteran of the action recalled that the mines were placed to break up enemy formations advancing in the dark. The pattern repeated across the war. Claymores went out before nightfall and came in before dawn or were detonated when something moved into the kill zone. A long range reconnaissance patrol moving into a night halt would establish a perimeter 10 to 20 m out from the wagon wheel of men sleeping back to back.
Trip flares went first. Claymores went second. In the highlands, LRRP teams developed a particular trick. They set a pinpulled hand grenade underneath each claymore so that if the mine was tampered with in the dark, the grenade went off and killed whoever was disturbing the wire. The men setting these traps had been trained in the practice because the people’s army had been observed more than once crawling up to American positions in the dark and turning the green cases around.
On February 19th, 1968, Sergeant Firstclass Fred Zabatski was on a reconnaissance mission inside Laos with a special forces studies and observations team. 60 enemy soldiers found the team. As Zabatosski fell back toward the landing zone, he rigged withdrawal. Claymores wired in series with white phosphorous grenades taped to the back of each one.
The pins pulled, the spoons held in place by the mine’s body. When the claymores detonated, the phosphorus grenades went up with them. Zabatosski radioed for an A1 Skyraider strike on the white smoke. 250lb bombs and napom came in on the smoke columns while dozens of pursuing soldiers were caught inside the fragmentation cones.
The team made it to the landing zone. Zabatosski received the Medal of Honor. That kind of use claymores as the breaking element of a withdrawal, as the silent partner of an air strike was beyond what the designers had at ajet had imagined. In the field, the weapon adapted to whatever the infantry needed.
It was daisy chained, one clacker, firing six mines at once. Soldiers rigged it to trip wires. They set it on the back blast side of a bunker to break a sapper team coming through the wire. Captain Dale Dy, a marine in Vietnam who later wrote about the weapon, said its employment was limited only by a soldier’s devious ingenuity.
The claymore’s most consistent work was the work nobody photographed. It was the moment in a perimeter defense when a wave came out of the dark and one man squeezed a clacker. At Firebase Illingworth on the night of April 1st, 1970, the 219yard perimeter held because every man on the line was on 100% alert.
Every claymore was in place and Captain John Ahern had pre-registered over a thousand rounds of supporting artillery. Of the 400 attackers from the 272nd regiment, dozens died inside the wire. The base was not overrun. There was an inverse case. A year later, on the night of March 27th, 1971, fire support base Maranne in Quantin Province was held by Company C, First Battalion, 46th Infantry of the 23rd American Division.
231 Americans and 21 South Vietnamese soldiers. The base had never been attacked. The battalion commander, Lieutenant Colonel William P. Doyle had a reputation for fighting and partying hard. The company commander, Captain Richard Knight, was 24 years old. The historian Max Hastings has documented what was happening inside the wire that month.
Men reading newspapers on duty, men playing cards without their rifles, one soldier dead from eating a piece of explosive he had cut out of a claymore in the belief it would produce a narcotic high. That night, the base had been under People’s Army observation for two months. Approximately 50 sappers from the 409th Vietkong Main Force Battalion, wearing nothing but shorts had mapped every bunker.
They came through the wire crawling on their fingertips. When they felt the trip flares, they used strips of bamboo from their teeth to tie down the strikers. When they felt the wires running to the claymores, they cut them. They cut 2/3 of the way through the concertina and broke the rest by hand so the wire would not sing.
At 2:30 in the morning, the mortars hit. By the time the men inside the base realized what was happening, the sappers were inside the wire. The claymores never fired. The tactical operation center burned. Captain Knight was killed. 30 Americans died and 82 were wounded inside about an hour of fighting.
the figures reconstructed by the historian Keith Nolan from declassified records and survivor interviews. He calls it the most blatant and humiliating defeat the US Army suffered in Vietnam. The weapon had not failed at Marannne. The men who held the wire had failed to use it. The Americans documented the weapon in service manuals, training films, afteraction reports, and memoirs.
The People’s Army did not publish equivalent records. What is known of how Hanoi viewed the weapon comes from captured documents and sapper doctrine reconstructed after the war. Sapper training included a procedure for the wire, fingertip probing through concertina, bamboo strips carried in the teeth to neutralize trip flare strikers, wire cutters to sever the firing wires running back to the bunkers.
It included another procedure as well documented in the captured material on People’s Army battle tactics. If a claymore could not be neutralized at the wire, it was to be turned reversed in place. The green case rotated 180° so that front toward enemy now read out toward the back of the perimeter.
When the American on the clacker squeezed, the 700 balls would fly into his own bunker. The People’s Army did not only counter the weapon, it copied it. In 1965, the Soviet Union introduced the M50, a rectangular plasticcased directional mine containing about 540 fragments propelled by 700 g of RDX explosive. It was the Claymore with different markings.
The Chinese fielded the Type 66, which copied the M181 down to the raised lettering on its face, the same instructional words in Mandarin. The Vietkong fielded the DH10, a handbuilt version mounted on a swiveing wooden frame packed with quarterin metal squares set in wax fired by a frictionpole igniter. The North Vietnamese fielded a domestic copy designated the MDHC40.
They scattered these on jungle trails. By 1968, American patrols in the central highlands were being struck by claymoreshaped weapons of wrong manufacturer. A patrol could be killed by its own design. What the communist forces left in writing was the practical respect.
The sapper doctrine, neutralize or cut or turn, survived intact in people’s army training manuals after the war. So did the Soviet, Chinese, and Vietnamese imitations. The M50 is still in Russian inventory. The Type 66 is still produced in the People’s Republic. The DH10 Lollipop in modified form was still being recovered from jungle floors decades later.
The silhouette of the weapon outlasted the war it was designed for. The Claymore is still in the United States arsenal. The Korean demilitarized zone is still strung with them. Ukrainian infantry on the line in 2026 are firing M181s shipped through Poland against Russian assault formations. The case is still gray green plastic.
The words on the front are still raised. The clacker still snaps. The list price of $119 in 1993 stood for decades. and nothing the army has built since then has done the job for less. The weapon outlived the country it was designed to defeat, the Soviet Union, and outlived the country it was first deployed in, the Republic of Vietnam.
What it did not outlive was the doctrine the People’s Army wrote against it, that the Green Case was the most dangerous object on the perimeter, and whoever found it first owned
