The Tunnels of Cu Chi (18 page)

   Stop the Americans!

By 1966, Vietnam had been at war with various enemies for nearly a quarter of a century. The Japanese had been followed by the French, and now the United States with its unimaginable power and fury had arrived. Within a year after the marines hit the beach at Da Nang, 850,000 tons of supplies were being hauled in every single month for the Americans, their ARVN allies, and the token troops from Australia, New Zealand, the Philippines, Thailand, and Korea. GIs ate some ten million field rations every month, used 80,000 tons of ammunition, and burned 8 million gallons of gasoline and oil. In May 1966 there were a quarter of a million GIs in Vietnam. The average soldier used up 340 pounds of food, clothing, ammunition, fuel, and supplies every day. Planes were being lost at the rate of one a day, at a cost of between $1 million and $2 million. There were now two famous American infantry divisions near Saigon, the 25th and the 1st. Included in their military tasks was responsibility for neutralizing the tunnels of Cu Chi. Each division needed $100 million worth of equipment to keep going, including 6,780 rifles at $122 each, eighteen light tanks, 362 jeeps, and four huge road graders.

In and around their two hundred kilometers of tunnels, the
Vietnamese were less well endowed with money or military hardware. The Cu Chi tunnels' defense system was evolutionary, owing its effectiveness to a mixture of tenacity, flexibility, and cunning. Its technology often reached back to the European wars of the Middle Ages.

Conventional defense for the tunnels was out of the question. The VC had neither the men nor the weaponry, nor was it ever the policy of the Communists in South Vietnam to face the Americans in large, fixed-location, set-piece battles. Anyway, tunnel-searching kept lots of GIs busy, a large investment with meager returns. Primary defense requirements were, as the Communist tunnels manual had stressed, camouflage and the maintenance of silence about precise tunnels location. Deaf and dumb villagers, the VC's equivalent of Sicilian Omerta, or silence, were the first line of defense.

Nevertheless, the tunnels did need a defense system; they could not be left unprotected at the mercy of every GI foot patrol that stumbled upon a tunnel entrance or telltale ventilation shaft. The slow development of a tunnel defense strategy eventually owed much to Captain Linh's careful observations of the Americans during Operation Crimp.

“They marveled at everything they saw,” he said, “everything seemed strange and new to them—the jungle, the fruits, the water buffalo, even the chickens. Again and again they would stop and stare, even pick things up. Not only were they easy targets for our snipers, but I realized the best way to kill them was with more booby traps. After Crimp we made more and more of them. I was sure they would work well for us.”

Despite the original shortage of explosive materials (soon remedied as the 25th Infantry began shelling Cu Chi), the homemade booby-trap business began to boom. Those with access to explosive powder, detonators, and a crude tunnel workshop, produced, first and foremost, the DH-5 or DH-10 mine. These were modeled on the successful American claymore mine, and were to be used primarily against the American light armored tracks and half-tracks, and inevitably, against unwary infantrymen. They were detonated either by pressure or—and this was a surprise—by command (remote-detonated). Major General Ellis W. Williamson, who commanded the 173rd Airborne Brigade, recalled vividly how he first got to hear about them. “We'd been in-country only a few
days when this young and overly excited lieutenant came up to me and says, ‘These mobile minefields are running us crazy.' He'd lost a lot of his men and he didn't know how to fight back. And I said, ‘Mobile mines, what are you talking about?' We'd studied all about mines, but nothing about mobile minefields existed in the literature. Now suddenly this lieutenant, right in the middle of battle, tells me the minefields are moving. A concept none of us had ever dreamed of. And he was right, absolutely right.”

Conventionally static, or earth-sown, minefields had been expected in Vietnam. What the general discovered was not just an isolated command- or remote-controlled mine, but a procedure by which the Viet Cong could not only detonate their mines electrically from a command center but also, if the enemy chose not to go sufficiently near the mines, physically transport the mines somewhere else. The concept of the “moving minefield” was another example of the optimum use of limited resources. A limited supply of mines went a long way under these circumstances.

The DH-5s and DH-10s were made out of crude steel, shaped like a saucer and containing five or ten pounds of high explosive. The mines stood on bipods pointing directionally, or they would lie buried a few inches underground. They inflicted dreadful injuries. One American medical officer's report explained:

Tunnel rat Lieutenant David Sullivan of the Big Red One recalled a particularly devious Viet Cong booby trap. A tunnel entrance would be exposed to lure the Americans. When a rat team was sent down to investigate, the guerrillas in the tunnel knew that other GIs would gather round the entrance for communication or on guard. A claymore mine hidden in a nearby
bush would then be detonated by wire from inside the tunnel. Sullivan lost several men like that: The VC waited until they heard the rats in the tunnel and then blasted the men still on the surface. In the confusion, the rats aborted the search, and the guerrillas escaped into the tunnel system.

One of the most feared variants of the DH-10 was the notorious Bouncing Betty, conical, with three prongs jutting out of the soil. When a foot struck a prong, a small charge was detonated, which shot the mine into the air about three feet, where it then exploded, showering shrapnel at groin level. It was a terrible mine.

For sheer ingenuity in adapting to local warfare conditions, a guerrilla farmer from the Cu Chi village of Nhuan Duc was to win the top award. To Van Duc invented a helicopter booby trap. It was known as the cane-pressure mine and for a while it was a successful (and to the Americans, quite baffling) answer to the problem of how to destroy the helicopters that brought troops and supplies into the jungle. At first, as the American heliborne assaults brought more and more troops to fight in the tunnel locations, the VC had tried with no success to lure the choppers into a booby-trapped landing zone. Inside the zone four hand grenades, each cross-linked by a friction fuse wire, would detonate in a daisy-chain sequence once the helicopter landed. But To Van Duc's invention was to that system what the space shuttle was to the Dakota.

Mindful of the simple physical principle that the blades of a helicopter create a considerable downdraft, the farmer suggested placing DH-10 mines at the
tops
of trees in an area where the helicopters could be expected to fly fairly low, or one to which they could be lured to fly low for surveillance. A highly sophisticated friction fuse was connected to the branches of the tree or fairly tall bush, which bent under the helicopter's downdraft, detonating the mine, which then exploded under the machine.

Confirmation of the efficacy of this system—and a reasonably successful attempt to counteract it—came from tunnel rat Captain Bill Pelfrey, the Special Forces officer attached to the 25th Infantry Division at Cu Chi. In December 1966, he was with a unit opening up landing zones for heliborne assaults. It was his company's mission to secure hot landing zones long enough for the helicopters to land. “Previously, we'd been
losing a lot of helicopters to mines and booby traps. They had a pretty ingenious little mine that they'd rigged so that when the helicopter tried to land, the wind from the rotors would shake the bush and that would set off the mine.”

He usually found these mines in bushes. “The mines were well camouflaged with foliage. The way you could spot them was this: If they'd been there a day or two, the foliage began to wilt and die, and you could spot the difference. When we found them we usually defused them by blowing them up with a small, quarter-pound charge.”

The mines and tunnel booby traps were cheap to make, psychologically effective, and did crude but considerable physical damage. One was a simple artillery shell dug into the ground and pressure-detonated by a man's body weight. “One of the regiment's battalion commanders stepped on a booby-trapped 155-mm shell,” wrote the medical officer. “They didn't find enough of him to fill a willy-peter bag [a waterproof sack little larger than a shopping-bag]. In effect … he had been disintegrated.”

By Viet Cong standards these were highly sophisticated traps. At the other end of the evolutionary scale of weapons were those that owed more to the Wars of the Roses than to the high-tech war in Vietnam. There was the crossbow and arrow, originally used by aboriginal tribesmen in the highlands to kill animals. It was adapted by the Viet Cong for tunnel defense. A concealed pit contained a bow with its ends embedded in the sides; an arrow was held under tension in the bow, and a simple release mechanism was activated by a tripwire running across the track. Historically contemporaneous was a medieval macelike device: a heavy mud ball with spiked bamboo stakes sticking out of it. This was attached to a tree by a seemingly innocuous jungle vine. When freed by the tripwire, the ball swung hard across the track.

Then there was the coconut mine, a hollowed-out nut packed with explosive powder and then covered by a rock as the missile—not lethal but scary. Or there was the bamboo mine. This was a large bamboo joint, cleaned out and filled with nuts, bolts, broken glass, or scrap metal, together with a small amount of plastic explosive or powder explosive. A friction fuse operated by a tripwire detonated this package.

The most common Communist booby trap was the wired
grenade, used in tunnel entrances or in the tunnels themselves. In the early days of the war the grenades were homemade, with wooden handles, or adapted Coke cans, with powder filled from dud U.S. shells. On jungle tracks and paths near the tunnels a favorite tactic was to place the grenade, with the safety pin removed, inside an appropriate tin can. A pull on the tripwire extracted the grenade from the can, which then automatically primed itself and exploded. Inside the tunnel a similar system would be used at the entrance or in the blackness of the tunnel itself. Often the tripwire was made out of jungle tree roots. The detonation of even a small grenade inside a tunnel caused unspeakable damage to anyone nearby and could cause an asphyxiating cave-in.

There was even the single-bullet trap, one cartridge held up by two bamboo pins, resting on a small wooden base, pressure-detonated by foot. And there were the infamous punji stick traps around all the tunnels. Sometimes the Viet Cong dug tiger-trap pits; if a GI fell into one, he became impaled on the spikes. The trap was kept to a reasonable size so that it could easily be camouflaged with twigs and foliage, but its depth was sufficient so that the victim's foot would descend with enough force for the stakes to pierce the toughened sole of the GI's jungle boot. A more sophisticated version had stakes buried in the wall of the pit, but facing downward, making extraction of the foot even more painful. Sometimes the sticks were smeared with excrement to aid infection, sometimes with a poison the VC simply called Elephant's Trunk, which they claimed caused death within twenty minutes of entering the bloodstream. There was even a bear trap, made out of poisoned punji sticks or metal spikes. The victim stepping on this would hit two boards, or steel plates with wooden and metal spikes attached. The boards would then pivot, burying the barbs into the leg just above the area protected by the boot. At face level, there was the bamboo whip, about five feet long with a fish-hook barbed spike at the end. This was held back taut by a wire linked to another cross-trail tripwire.

Sometimes the Viet Cong resorted to original if somewhat gruesome local psychological warfare. On one occasion following an American attack on a tunnel complex, Captain Linh watched impassively as a GI, alighting from a tank, stepped on a DH-5 mine, which blew the unfortunate soldier's leg off.
After the man had been “medevaced” and the patrol left, Linh retrieved the leg. On a discarded American C-ration box he wrote the word “dangerous” in English, then hung the leg and the sign on a tree that had been defoliated by shelling. For effect, he added a skull and crossbones. It was during the dry season, and the shriveled leg hung there for several weeks, acting, Linh claimed, as a useful deterrent.

There is some evidence, tantalizing but inconclusive, that the Viet Cong may have tethered bubonic-plague-infected rats in the tunnels as a primitive form of biological warfare against the GIs who went down to explore the complexes. Early in March 1967, a foot patrol from A troop, 3rd/4th Cavalry, of the 25th Infantry Division, entered a tunnel in Hau Nghia province, about one mile northwest of Cu Chi town. Inside they found three dead rats, all leashed round the neck. A syringe and phial containing a yellow fluid were also found, together with cages for catching the rats. The patrol commander immediately contacted intelligence specialists attached to the 521st Medical Detachment (Intel), who took over the analysis of this bizarre find. One of the rats was found to be a carrier of bubonic plague.