|Whenever a unit arrived at a new destination it would
immediately start preparing defensive fighting positions. If in a village,
Squads would be assigned to houses and sectors of the perimeter.
Villagers were not allowed to leave the area and reconnaissance elements
would set up outposts along likely enemy avenues of approach.
Sites were selected according to strict criteria: had to provide good defensive terrain for the defenders while at the same time offering little protection for an attacker; dense overhead cover was sought in order to protect the site from aerial observation; it was important not to have physical obstacles likely to prevent or hinder a quick, safe withdrawal.
Two defensive belts of fortifications were constructed approximately 50 to 200 meters apart depending on the terrain in the shape of an L, U or V in order to offer interlocking lines of fire.
Fighting positions were L-shaped with an open trench at one end approximately 1.2 meters long and deep by about 0.5 meters wide. Dirt excavated from the trench was piled in front of the position with an embrasure left as a firing port. At a right angle to the trench was a bunker 1 meter long by 0.5 meters wide with a roof of tree trunks and earth up to 0.5 meters thick. Trenches deep enough to conceal a crouching man were dug to connect the individual positions with combined fighting holes and bunkers.
Using these positions the defenders could fire upon an advancing enemy, thus forcing them to withdraw, and then take refuge in the covered portion of the bunker when the inevitable air or artillery support arrived, only to re-emerge when the enemy infantry resumed it's assault.
It was important that the second line of positions not be visible from the first line of positions and the distance between the two belts was dictated by terrain sufficient to accomplish this. The second line of defense provided a protected position to which the first line of defenders could withdraw. From the second fighting line they could then withdraw further from the contact area or they could counterattack to take back the first line of defenses - a tactic known as 'rubber banding'. This system also meant that allied forces which had taken the first belt of defenses still had to advance further in order to engage the second line and were denied the opportunity of using the captured fortifications as a position from which to launch their assault.
The 'two belt' defensive system was cynically employed by the NVA and the VC when the site chosen was a village or hamlet. The outer belt would be positioned outside of the village boundaries while the inner belt was constructed within the village itself using bunkers and protected positions integrated into the village structures. US Rules of Engagement prohibited the use of heavy weapons and Air/Artillery supporting fires within 1000 meters of inhabited areas in order to avoid civilian casualties and collateral damage and in order to utilise fire support of this nature clearance was required from higher military and often civil authorities.
It was not uncommon for dummy fighting positions to be constructed, designed to be spotted by aerial observers, with a view to drawing away US artillery and air attacks from the main defensive positions or at least requiring the US to expend ordnance and troops better employed elsewhere.
In remote jungle bases, which were usually out of the range of US artillery and sufficiently isolated so as not to be the target of frequent US sweeps, semi-permanent base camps were developed which consisted of extensive defensive fortifications. Base camps followed the same two-belt design as smaller sites but with two major differences - a third belt was added in the larger camps and fighting positions and bunkers were larger and better protected. Base camp bunkers were typically 8' by 5' , with a depth of between 3' and 4' and covered by a two feet thick layer of logs and dirt. Small entrance ways at either end of the bunker doubled as firing ports. Trenches connected the fighting positions within a belt as well as those to the rear and hence offered protected avenues of withdrawal.
The US answer to these positions was to surround them and then lay on artillery, air and helicopter gunship attacks. The VC/NVA attempted to counter this by 'hugging the belt' of the enemy, that is, attempting to stay in very close proximity to the US troops in order to prevent the use of air and artillery supporting fires due to the proximity of friendly troops. Another tactic was a simple but well executed counter attack.
It should be pointed out that invariably the objective of the VC/NVA forces was to withdraw, break contact and live to fight another day. Unless they were initiating the combat, which would always be done under favorable conditions of terrain and numbers (see Offensive Tactics), the VC/NVA always tried to avoid combating US troops in circumstances which were anything less than favorable. The tactic of counter attacking would only be used against a numerically inferior enemy force or, as in the case of the ARVN, against a force which was poorly motivated, led and supported.
Inside the VC and the NVA by Michael Lee Lanning & Dan Cragg, Ivy Books, ISBN 0-8041-0500-6