An NVA/VC force of any size could execute an ambush although the size and sophistication of an ambush varied from hasty meeting engagements to full scale, carefully planned, regimental sized ambushes that included forces sufficient to encircle the enemy in the kill zone. In instances where smaller units didn't have enough troops to stage a complete five-element ambush they would set up one of the preferred ambush types and avoided close assaulting the enemy.
The preferred time for ambushes was just before dark. Enemy units were often deliberately delayed by the deployment of small patrols or snipers which harassed it. Roads and bridges to the rear of the enemy unit would also be sabotaged or mined to prevent withdrawal. This limited the enemy's use of air support and the deployment of reinforcements. It often also resulted in the ambushed unit being pinned in place for the night and having to set up an NDP in a hostile area.
All ambushes, in keeping with universal ambush doctrine, were intended to inflict maximum casualties on the enemy and to allow the ambushing force to withdraw before effective fire could be returned.
This depended on the use of command-detonated mines which were triggered by hidden troops who held a detonating device connected to the demolitions by electrical wire. Mine ambush kill zones might also include punji traps or other homemade traps, land mines and natural obstacles. However, the ambush was always triggered by electrically detonating a mine, when enemy troops moved within the mines killing range.
Used by small units against larger enemy forces as a means of harassment, delay and disruption. By positioning the ambush to enfilade an avenue of approach, the NVA/VC obtained more effective results. Minefields, mantraps, and booby traps were placed along both sides of the trail and perpendicular to it. As the enemy unit came under fire and attempted to maneuver right or left to close with the ambushers, the protective barriers would inflict casualties. As soon as the ambushing element realised that the enemy had advanced into, and taken casualties from, the mine/trap line, the ambushers withdrew to another pre-selected site where they might repeat the maneuver.
This was one of the simplest to set up and operate and was most commonly used by the NVA. It was also easy to get into and away from quickly. The ambush position was laid parallel to the target area. Mines or other obstacles were placed on the other side of the ambush site. Upon command, fire was brought to bear on the kill zone from multiple, overlapping firing positions. The linear ambush pumped bullets into the flank of a surprised enemy column.
L-shaped ambushes included the most effective aspects of both the 'Bloody Nose' and Linear ambush. The short end, or base, of the 'L' was positioned so that at least one machine gun could fire straight down the kill zone, enfilading it. Parallel to the kill zone and tied into the 'L' was a second, flanking ambush.
The 'L' shaped ambush could also provide it's own flank security. The base of the 'L' might be placed along either flank of the ambush position, not to fire into the kill zone, but to ambush enemy units that were attempting to flank the main ambush position along obvious avenues of approach.
In some situations the enemy located a reserve unit in line with the vertical bar of the 'L' forming a 'T' ambush. After the ambush was sprung, the enemy maneuvered his reserves to block the enemy line of withdrawal. The reserves either close assaulted or set up another ambush along the first linear obstacle to the immediate rear of the kill zone.
The following account is a good example of a typical VC "L" shaped ambush action. The success attained by friendly forces can be attributed to rapid and aggressive reaction, and the use of the reserve against the enemys weak flank.
This was usually directed against a road bound column of vehicles. The NVA/VC usually sprung it out of high ground, near a bend in the road, which allowed cover and longer fields of fire for automatic weapons. Weapons frequently opened fire from positions within forty yards of the road, or less.
A road bend was included in the kill zone so that the end of the column was out of sight of the head of the column when the ambush was sprung. Interruption of a column's front-to-rear line of sight increased the likelihood that the head and tail of the column would split and try to fight separately.
The ambush was initiated by a small element striking the head of an enemy column and stopping it by fire. Then the main body would attack the column from the rear and/or flank, fragmenting it and rolling it up. The two strikes were timed close enough together so that the target column was engaged from both ends before it could deploy and face toward either danger.
Positioned with its open mouth toward the enemy advance, this was a favourite of the VC. It was used in both fairly open terrain as well as jungle. The ambushers, in good concealment along the legs of the 'V', would wait until the enemy point had passed and then creep close to the trail. The 'V' ambush was virtually undetectable by enemy point or flank security until at least a portion of the enemy force was in the kill zone. Enfilading fire was often directed down the enemy axis of advance, and interlocking fire from each leg across the 'V'. The 'V' ambush also lent itself to the use of controlled mines and booby traps.
Usually laid along a road, the 'Z' ambush was both effective and confusing to the unit being ambushed. This complicated ambush was usually well planned with low bunkers lining the kill zone, often prepared months prior to the ambush. The ambush position was only occupied after word was received that an enemy battalion or larger unit would be using the road, which passed through the ambush site.
The long end of the 'Z' ambush was located on one side of a trail or road enabling the ambushers to employ both enfilading and flanking fire. It was also placed to neutralise attempts to flank the ambush from nearly every direction. Ambushing units deployed along the two short ends of the 'Z' could fire in either direction. The 'Z' ambush was dangerous to ambushers because ambush elements could easily fire into each other.
Secrets of the Viet Cong J W McCoy, Hippocrene Books 1992, ISBN 0-7818-0028-5
Inside the VC and the NVA Michael Lee Lanning & Dan Cragg, Ivy Books 1994, ISBN 0-8041-0500-6