The Tunnels of Cu Chi (10 page)

Vietnam is primarily an agrarian society. It is not a land of important cities or towns, nor does it have an urban-based technology. Vietnam is a land of peasants, whose deeply traditional lives are characterized by constant repetition, by the sowing and reaping of rice and the maintenance of customary law. The Vietnamese worship their ancestors as the source of their lives, their fortunes, and their civilization. In the rites of ancestor-worship the death of a man marks no final end. Buried in the life-giving rice fields that have without break sustained his family, the father lives on in the bodies of his children and grandchildren.

In this continuum of the family, personal possessions and private property hardly exist. The father is less the owner than the trustee of the land, which will beyond doubt be passed on to the children. To the Vietnamese, the land itself is the sacred, constant element. Western concepts of land-profiteering, of mobile societies, of land development or neglect, are beyond comprehension to the Vietnamese peasant. For the traditional villager, who spends his time in one place, bound by long tradition to the rice land of his ancestors, the world is a small place. The earth takes precedence, for as the source of life, it is the basis for the social contract between the members of the family and the hamlet or village. Without land, the villager would have no social identity; he would be a tramp, a landless vagrant. The people believe that if a man moves off his land and beyond the village limits, his soul stays behind, buried deep in the earth with the bones of his ancestors.

It was never military necessity alone, nor indeed the suitability
of the local terrain, that led to the creation of the tunnels of Cu Chi; these were crucial factors, but it was also shrewd tactics for the new Communist cadres, returning south in the early sixties, to plan a life underground—an existence of both practical and symbolic significance. Strategy demanded it, the soil allowed it, and above all, history positively encouraged it. If, as General Vo Nguyen Giap believed, the enemy was to occupy the face of his earth, then his people would occupy its bowels.

For the Communist engineers, the cadres, and the peasants, the soil of Cu Chi had a huge natural environmental advantage for tunneling. Owing largely to its proximity to the nearby Saigon River, it is predominantly laterite clay, a ferric soil with a clay binder, which allows some air penetration. According to Engineers Corps Lieutenant Colonel Jerry Sinn, who examined the tunnels in detail in Cu Chi in the autumn of 1969, the clay was not particularly affected by large changes in the amounts of water present in it, and was consequently a remarkably stable structure for tunneling. It was further strengthened, rather like reinforced concrete, by the roots of various trees, a natural construction system the Americans called over-birth. “It was a super tunneling dirt,” said Jerry Sinn gloomily. Captain Linh put it even more simply: “The earth in Cu Chi is sticky and doesn't crumble. The area is fifteen to twenty meters above sea level and for some six meters down we knew there is no water. The water table was usually found at about ten to twenty meters. We could not have expected better conditions.”

Dry laterite clay has a dull reddish appearance. During the dry season in Cu Chi, the top surface along the village roads becomes a gritty dust, as uncomfortable and penetrating as sand. Yet the texture of the laterite clay round the tunnels was as hard as brick and seemingly impermeable.

There was nothing new about the use of tunnels by defenders against attackers. Indeed, Chinese guerrillas had successfully used tunnels in Hopei province during the Japanese war in the thirties. Whole counties were linked by underground defensive and communications networks. For the West, trenches and tunnels recalled the nightmare of World War 1, of mud and gas and death by the thousands as men were caught in holes in the ground by gas and artillery fire. Extensive tunnels,
built by the Korean and Chinese forces across the waist of Korea near the 38th parallel, were widely used during the Korean War in the early fifties. However, never before had so daring a plan been conceived, as a result of which central government authority simply did not extend to a huge area of seventy square miles just outside the nation's capital. The tunnels made Cu Chi a no-go area by night and effectively out of bounds by day, without the use of extensive military support. It was as if Washington's authority did not reach to Philadelphia, or London's writ to Croydon.

The basic tunnel infrastructure, dug in the mid forties, had been little more than a series of backyard shelters and short interlinking hamlet communication tunnels. The tunnels of the sixties, however, were to be far more than convenient hidey-holes, safe houses for the Communists, or secure weapons caches. They were to be the linchpin of the entire regional campaign, and they would have to survive the high-tech assault of the most powerful and sophisticated military machine in the world.

On 28 September 1967, a detachment of the Korean 28th Infantry Regiment of the 9th (South Korean) Division captured a remarkable enemy document during a sweep north of Saigon. A full four months later it was translated into English and handed over to the American Defense Intelligence Agency and all the appropriate senior command structures in Vietnam. But by the time it had reached down to unit command levels in early 1968, it was almost too late in the war to be of much help. The Tet offensive was imminent and the fundamental nature of the land war would soon change. The document appears to be, on internal evidence, the only tunnels manual ever issued by the Communists. It is a ten-page technical and political booklet, revealing many secret details about the tunnels' structure and strategic purpose. The anonymous author displays the party's hopes and fears for the future of tunnel warfare in a style that reflects the authority, naïveté, and patronizing attitude that generally characterized the relationship between senior regional cadres and their village equivalents.

The
primary
role of the tunnels is stressed and restressed. “They are for the strengthening of combat vitality for our villages. They also provide more safety for our political and armed units, and for the masses as well. But their sheltering purpose
is only significant when they serve our soldiers in combat activities. As mere shelters, their great advantages are wasted.” And, even more significantly: “There must be combat posts and equipment inside the underground tunnels for providing continuous support to our troops—
even if the enemy occupies the village
.” The document mixes political exhortation with what was to become a shrewdly accurate prediction:

The tunnels would be crucial for launching close-in attacks on the Americans and would also provide opportunities to seize their weapons; they would provide excellent mobility and (as the unlucky 25th Infantry Division was to discover) “we may attack the enemy right in the center of his formations or keep on fighting from different places.”

Nobody, not even the centralized Hanoi planners, could predict the course of the war in Military Region IV, the area surrounding and including Saigon, from 1965 onward. To that extent the construction of the tunnels involved considerable extemporizing and engineering empiricism. The captured Communist tunnels manual envisaged a fairly rigid infrastructure, determining precise dimensions for tunnels and chambers and trapdoors. That the system grew and developed as it did, well beyond the original vision of this manual, is, perhaps, a testament to some residual sense of free enterprise among the builders. But at the outset, as the captured document reveals, the system was to be simple and effective: “We must plan for the eventual impossibility of fighting from inside the underground tunnels. A secret passage must then be available from which our troops may escape and fight in the open, or reenter the underground tunnels if necessary.” The passages of the tunnels were not to be either straight or “snakelike,” but were
to zigzag at angles of between 60 and 120 degrees, “because if the enemy detects the entrance to the underground tunnel, he will set off mines and banglores (chain explosions) or pour in chemicals, both of which are certain to have disastrous effects on our troops.” In fact, the use of explosives and chemicals did not have “disastrous effects”; zigzagging, however, did make a straight line of fire inside impossible, and helped deflect explosive blasts.

The dimensions of the communicating passages were clearly laid down. They were to be no wider than 1.2 meters, no narrower than 0.8 meters, no higher than 1.8 meters, no lower than 0.8 meters. The minimum thickness of the roof was to be 1.5 meters—“to avoid vibration caused by the explosions of bombs and shells and the sounds of mechanized units moving above.”

A clever and finely engineered trapdoor system was devised by the Communists to create entrances and exits to secret passages and from one tunnel level to another. Where the water table allowed and local conditions necessitated it, tunnel complexes of as many as four separate levels were built. This remarkable feat was a tribute not only to the stamina of the diggers but also to their extraordinary practical application of certain physical principles, which allowed people to stay alive for years deep inside the ground, because the very rudimentary life-support measures actually worked. Air, sanitation, water supplies, and cooking facilities were sufficient to maintain a primitive but reasonably safe existence. It was crucial to the whole plan that even if the first tunnel level was discovered, the secret trapdoor that led down to the next would remain hidden from the enemy. That meant making trapdoors that were virtually invisible.

One of Captain Linh's favorite displays is to take guests into the underground by the Phu My Hung tunnel complex, stand them in a circle about twenty feet in diameter, and challenge them to find the tunnel trapdoor within that area. No one has ever done it. Linh then stamps on the ground and suddenly a grinning comrade lifts the trapdoor and pops out. The point is made. Only the most laborious, time-consuming, and dangerous probing with knife or bayonet would reveal a good trapdoor. The blueprint for trapdoor construction laid down by the manual was as follows: “With boards 1 cm thick and 2–3
cms wide, make two frames, one with horizontal boards and the other with vertical boards. Insert a nylon sheet between the two frames, which later will be glued together. Cover it with sponge rubber and fill all openings with wax. A single board should never be used for a frame [trapdoor] because it is not strong enough.”

The sides of the trapdoor were usually beveled downward at an angle so that it could take considerable over-pressure. There was no sag. If the trapdoor was inside the tunnel, the VC placed earth on top of it and hid in the earth small finger wires, which allowed a soldier to lift the door. If the trapdoor was outside, then small plants would be encouraged to grow on it, or dead foliage would be cunningly “planted” to make it as one with its environment.

Ventilation holes were simplicity itself. They ran obliquely from the surface to the first level—obliquely to avoid monsoon rain flooding in. Some always pointed east toward the preferred light of a new day. Others, by instruction, “must be turned toward the wind.” In the deathly blackness of the tunnels, these ventilation holes were to be the only physical reminder of the existence of the real world, with air and light, a few feet above. Internal ventilation holes were bored down to the lower tunnel levels.

Entrances to the tunnels were carefully and precisely engineered to cater for various contingencies. The Communists' tunnels manual explained:

The entrances also had to be able to resist fire, flood, and chemical warfare: “for this reason, we must locate the entrances to the tunnels in dry, elevated, and well-ventilated areas. Such an entrance will not be blocked by the chemicals that will otherwise kill the occupants. Also rainwater will not stagnate in the entrance so located.”

The three trapdoors in the triangular entry system were to be an average of forty to fifty meters apart, and the entrances were to be strong. “We need to expend a great deal of manpower, time, and materials to make them so. The following dimensions are to be adopted: square entrance 1.5 meters for each side, rectangular entrance 1 meter × 1.8 meters, round entrance 1.5 meters in diameter.” The authors of the captured document went on to complain:

The attention to detail is dogmatic, but the fact remains that the tunnels of Cu Chi were the primary factor in fighting the campaign against the Americans, and if sloppiness or engineering imprecision infected the building of the system, the Communists would lose. Some first-hand evidence of the stability and efficiency of the Cu Chi tunnel system fell into American hands when a VC guerrilla, Ngo Van Giang, was captured by the South Vietnamese on 31 January 1968. In a sixteen-page debriefing statement, Giang is quoted at length by his interrogators on the subject of the Cu Chi tunnel network. He told his captors that where a tunnel became an open bunker, special roofs had been constructed by using 50-cm-thick bamboo poles followed by another 50-cm-thick layer of “husks.” Then there was a layer of dirt 50 cm thick. On top of the dirt, they had planted flowers or used fallen trees as camouflage. Incredibly, according to Giang, if a 200-kg bomb fell within just ten meters of the tunnel, no damage would result. The husks and leaves used were excellent protection against bomb blast. Bamboo poles were also employed for their resilience. “In April 1966,” Giang told his captors, “an airplane dropped
a 200-kg bomb at Chua hamlet, and the bomb hit right on this type of tunnel. The dirt and husks caved in, but the cadre [inside] was not wounded.”