What the Viet Cong and the North Vietnamese Army lacked in the way of firepower they made up for in ingenuity. Concealed devices used to inflict casualties, booby traps were an integral component of the war used by Viet Cong and the People's Army of Vietnam. These devices were used to delay and disrupt the mobility of Australian forces, in fact, the threat was often enough to slow any advance to a snail's pace, divert resources toward guard duty and clearance operations, inflict casualties, and damage equipment. They were a key component in prearranged killing zones. Booby-traps could be covered by snipers to further annoy the enemy or they might be the signal to spring an ambush.
The use of booby traps also had a long-lasting psychological impact on Marines and soldiers. The fear of booby traps was so great that units in the field were under stress the whole time. This created severe mental fatigue on both the commanders at platoon level and the individual soldiers.
Many of the materials for the mines and booby traps were of U.S. and Australian origin. These included dud bombs, discarded and abandoned ammunition, munitions and indigenous resources such as bamboo, mud, coconuts and venomous snakes.
The imaginative use of booby traps by the North Vietnamese Army and the Viet Cong caused many casualties amongst their opponents. Between January 1965 and June 1970, 11% of the fatalities and 17% of the wounds among Australian Army troops were caused by booby traps and mines.
Booby traps can be divided into explosive and non-explosive antipersonnel devices and anti-vehicle for example, tank, vehicle, helicopter, and riverine craft devices. Antipersonnel booby traps were concentrated in helicopter landing zones, narrow passages, paddy dikes, tree and fence lines, trail junctions, and other commonly traveled routes. Anti-vehicle booby traps were deployed primarily on road networks, bridges, potential laager positions, and riverine choke points.
Non-explosive Booby Traps
Non-explosive antipersonnel devices included punji stakes, bear traps, crossbow traps, spiked mud balls, double-spike caltrops, and scorpion-filled boxes.
By far the most common types of booby trap was the single punji stake. Punji stakes were sharpened lengths of bamboo or metal with needle-like tips that had been fire-hardened. Often they were coated with excrement to cause infection. Dug into shallow camouflaged holes and rice paddies and mounted on bent saplings, this was a common booby trap. Another similar device was a spiked mud ball suspended by vines in the jungle canopy with a trip-wire release. It functioned as a pendulum, impaling its intended victim. The simplest pit type was a hole about 20 to 30cm deep. The floor of this trap was then set with punji stakes which could easily pierce the canvas and leather jungle boot. For added misery the spikes could be smeared with poison or human excrement to induce blood poisoning or worse. There were many variations which allowed the spikes to attack the sides of the leg. This was particularly favored after the introduction of the reinforced soled jungle boot.
Punji traps were laid wherever the enemy soldiers were likely to land with force. The purpose of the pit was to increase the downward force of a walking man. Such places included the places that soldiers would throw themselves to escape gunfire, ditches, behind logs, in long grass etc; or where they would land with some force, stream banks, likely helicopter landing zones etc. Side closing traps were also to be found. These ranged from the same size as the punji pit up to man-sized traps. These were more sophisticated versions of the punji pit and were likewise smeared with excrement or poison.
The second group of non-explosive traps used some form of mechanism to set them off, usually a trip wire. The wire could be stretched across a track as a delaying tactic or linked to a hidden man to be released on command as part of an ambush or to hit a selected target.
The swinging man trap was positioned on jungle trails and heavily camouflaged. It comprised a weighted beam pivoted so that when the pressure plate was pushed down the other, spiked end swung upwards with enough force to impale the victim. The target area was the chest in order to inflict a messy fatal wound.
The bamboo whip was encountered on trails and was set off by a tripwire. It comprised a length of bamboo under tension and set with spikes at chest height. The unfortunate victim would receive severe, if not fatal, wounds to the chest as it whipped across the trail
The spiked ball was another trap designed for jungle use. It was sprung by a trip wire which released the heavy clay ball set with sharp spikes. The force of gravity and the height of release combined to inflict horrific, usually fatal, wounds in the head and shoulders region. The bow trap was a favorite in the heavily forested mountainous areas, though it was not limited to these. It too was tripped by a wire which released a tensioned bow set in a shallow pit. The target area was the leg. The arrow was normally tipped with poison or human excrement.
Explosive Booby Traps
Variations of explosive antipersonnel devices encompassed the powder-filled coconut, mud ball mine, grenade in tin can mine, bounding fragmentation mine, cartridge trap, and bicycle booby trap. The mud ball mine was a clay encrusted grenade with the safety pin removed. Stepping on the mud ball released the safety lever, resulting in the detonation of the mine. The cartridge trap was a rifle round buried straight up and resting on a nail or firing pin. Downward pressure applied to the cartridge fired it into the foot of the intended victim.
These were normally set to give warning of an approaching force or as part of an ambush. They were also employed to slow down a follow-up force after an ambush or to cover a withdrawal. The generally poor quality of the grenades used by the Viet Cong and North Vietnamese Army combined with their long fuse of 5-6 seconds made them much less effective than they might otherwise have been. The grenades were placed in tubes of bamboo or tins to keep the safety lever from releasing when the pin was pulled. The victim tripped the wire, set at whatever height, pulling the grenades from their containers.
Command detonated grenade daisy chains were set along trails where patrols were likely to be. These grenades were set close together to inflict casualties at a point where there would be a bunched target. Grenades were also set in the ground below gates so that the slightest movement of the gate would detonate it right below the victims' feet. In areas where the vegetation closed above the trail grenades were often set to shower splinters of wood and metal downwards, causing messy wounds which would require urgent casualty evacuation.
Dud shells and bombs were salvaged and turned into traps. The shell most commonly available for this was the 105mm artillery shell. The tip of the bullet just protruded from the earth. A foot would press down sufficiently to set it off. The bullet would explode shattering the victim's foot. If he was unfortunate enough to be wearing the reinforced soled jungle boot then the steel or plastic plate turned into shrapnel. The grunts called these toe poppers. They were usually set in long grass.
Traditional anti-personnel mines of all sorts from WW2 vintage onwards were used as they were intended and as part of booby-traps. One of the most common, and most hated, was the Bouncing Betty. These mines were triggered by the release of pressure on the arming mechanism. Thus a soldier could stand on one, hear the arming mechanism operate and freeze. There he was standing erect knowing that if he moved his foot the mine would jump into the air and explode at chest height. Combat engineers came up with many extemporized methods of saving trapped soldiers.
The Viet Cong and North Vietnamese Army did not booby trap souvenirs to the same extent that the Japanese and Germans did in WW2. They did do it, but it was uncommon and possibly the more effective for that.
Anti Vehicle Traps & Mines
Anti-vehicle devices included the B-40 antitank booby trap, concrete fragmentation mine, mortar shell mine, and oil-drum charge. The B40 was a rocket propelled antitank grenade, which in this instance was placed in a length of bamboo at the shoulder of a road and command fired at a vehicle crossing its forward arc. The mortar mine was simply the warhead of a large-caliber mortar that had been separated from its body and retrofitted with an electric blasting cap. The oil drum charge was based on a standard U.S. 5 gallon oil drum filled with explosives and triggered by a wristwatch firing device. This booby trap had immense sabotage applications for use against fuel dumps.
Soft vehicles could be destroyed by several of the anti personnel mines or booby traps described above. The Viet Cong and North Vietnamese Army used large numbers of mines to destroy enemy. The crew of all vehicles would attempt to reduce the effectiveness of mine blast by putting layers of sandbags on the floor. This naturally affected the mobility of these vehicles. Some M113's and M551's were overloaded by doing this.
Anti Helicopter Traps
As the war progressed the prediction of likely helicopter landing zones became an art at which the Viet Cong and North Vietnamese Army became adept. The edges could be trapped or mined and heavy machine guns were targets. However, a booby trap for helicopters consisted of wires connected to grenades atop posts at the edge of the landing at a height to inflict blast and splinter damage on the troops and splinter damage on the helicopters themselves, with the rotors being particularly vulnerable. Another particularly nasty anti-helicopter trap was the claymore mine sited on it's back to fire up into the air as the helicopters were on final flare, sending hundreds of steel pellets through the soft belly of the helicopter. Still other mines were rigged into the tops of trees to be detonated by the rotor wash of nearby helicopters.