Professional Knowledge Gained from Operational Experience in Vietnam, 1969, Special Issue, Mines and Boobytraps

1. What they did

This United States Marine Corps manual collects what Marines learned in the Vietnam War, up to 1969, about enemy mines and boobytraps. It was first issued in mid-1969 and reprinted in 1989 for junior officers and non-commissioned officers, to complement training manuals on patrolling and small-unit tactics. It is a training reference, not a research study.

It has four sections:

• Enemy mine warfare. How the Viet Cong (VC) and North Vietnamese Army (NVA) obtained materials, ran mine factories and chose where to place devices.
• Countermeasures. What units and individual Marines could do to find, avoid and destroy devices, and what to do when one is set off.
• Enemy mine indicators. Illustrated examples of the markers the enemy used to warn their own people where devices were placed.
• Enemy mines and boobytraps. Illustrated descriptions of explosive and nonexplosive devices against people, vehicles and helicopters.

2. What they found

Why it mattered

• In the first months after Marines landed in South Vietnam in March 1965, about 65 to 75% of Marine casualties were caused by mines and boobytraps. In 1968 the figure was 37.7%, more than one in three Marines killed or wounded.
• About 90% of the material in enemy mines and boobytraps was of U.S. origin: dud and abandoned ammunition and carelessly discarded trash such as ration and drink cans.

Where devices were placed

• Any place a Marine often walks, takes cover, rests or draws water: narrow passages, paddy dikes, trail junctions, hedgerows and tree lines, fence lines and gates, branches over trails, shady areas, stream fords, wells and likely landing zones.
• Vehicle mines were placed at road junctions, near bridges, in potholes and in old wheel and tread tracks, with care taken to remake the track afterwards.

Reading the ground

• The manual calls an alert and observant Marine, who knows where to look and what to look for, the best mine and boobytrap detector the Marine Corps has, better than electronic devices or dogs.
• Marines are told to look for things that “just don’t look right”: mud smears or dung on the road, signs of recent digging or repair, wires leading away from a road, tripwires, and terrain that does not look natural. Cut vegetation dries and changes colour; rain can wash away a covering and leave a surface depression; a covered device may show as a mound.

Enemy markers

• Markers were usually set in a regular pattern, such as sticks or stones in a line, and this regularity was the danger signal. Any arrangement of sticks and stones that looked unnatural meant devices were likely nearby.
• Examples include three-stick arrowheads (which do not always point towards the device), bamboo rectangles and tripods, bamboo stuck in the ground at 45 degrees, broken saplings or bushes, folded banana leaves pinned with a thin stick, tied tufts of growing grass, forked sticks, rock formations, crossed sticks or stones on vehicle tracks, and three spaced sticks across a trail. Short sticks laid parallel to a trail usually meant the trail was clear.
• For many markers, the distance to the device was unknown or varied, from directly under the marker to 400 meters on.

Scouts and dogs

• Kit Carson Scouts, using their native ability and knowledge of the area and of VC activities, found 229 mines and boobytraps in October 1968 in one Marine area.
• Specially trained scout dogs detected the scent left by the person who placed a device, for 1 to 4 days afterwards. They also used sight to spot tripwires and unnatural objects, and hearing to pick up tripwire vibration; many felt a tripwire with the hair of their forelegs or chest and backed away. Of 119 dogs killed in South Vietnam since January 1967, only seven were killed by boobytraps.

3. What they concluded

• Despite all the detection devices developed, experience showed that an alert Marine, aware of what to look for and where to look, is the most effective detector.
• Cutting off supply (destroying duds, not abandoning ammunition, destroying trash) and destroying mine factories were the most effective ways to remove the threat at its source.
• Avoiding patterns was central: stay off trails and footpaths where possible, vary routes and timings, move where local people move, keep 15 meters between men, and move slowly.
• Every Marine should be trained in visual detection, the buddy system, dispersion, demolition and immediate action drills.

4. How tracking was or was not used

The manual does not use the word tracking, but much of it is about reading signs of human activity on the ground. Marines are taught to notice disturbed soil, drying cut vegetation, depressions, mounds, wires and out-of-place objects, and to recognise deliberate markers by their unnatural regularity. Scout dogs followed the scent of the person who placed a device. The manual also warns that the enemy exploited the Marines’ habit of following old vehicle tracks by placing mines in them.

5. Tracker or observer certification

Reported but not validated. Kit Carson Scouts are credited with native ability and knowledge of the area, and scout dogs are described as specially trained, but no test of their skill is reported. Marines’ visual detection relies on unit training; no standard of skill is given.

6. Other technologies, skills or innovations

• Portable ground radar and seismic intrusion devices.
• Mine detectors (AN/PRS-4 and another model), with notes on their limits: gravel, metal debris and deeply buried or non-metal mines caused false or missed targets, and operators tired after about 20 minutes of wearing earphones.
• Probing suspicious spots with a probe or bayonet, and feeling for tripwires with a light bamboo stick or slender steel rod.
• A Volunteer Informant Program that paid local people, many of them children, to turn in dud and abandoned munitions.