VC and NVA breakthrough, or power raids, often caught the allies by surprise. In many cases allied defenders were unaware of the enemies presence until it was too late. Sometimes they could hear NVA and VC fire support elements digging weapons positions within fifty to one hundred yards of their perimeter just before an attack. What they did not not often realise was that those sounds meant that the enemy sappers had already begun to infiltrate and neutralize their base's barbed wire and mined approaches along a narrow front.
The defenders of the Base Camp usually came to realise that they were under attack only after heavy direct and indirect suppressive fires began to hit specific targets along and inside of, the defensive perimeter. Mortar, recoilless rifle, and machine gun fire was directed against selected bunkers and other defensive works. Other mortar fire fell on the interior of the position, discouraging deployment toward the threatened sector.
Supporting fires provided cover for a small breaching detachment, usually composed of elite sapper troops, which systematically breached all mine and wire barriers . Cutting narrow lanes in the defensive barrier, the sappers moved rapidly toward the nearest bunker or firing position, whose fire could command the breach. They destroyed bunkers with B-40 rockets, satchel charges and grenades.
Following on the heels of the sappers was the main assault force, running forward firing from the hip, straight for assigned objectives.
When attacking an enemy post or fire base, the NVA/VC were guided by a specific power raid doctrine;
the attacking force had to be superior to the defending force
the assault force concentrated its power along a single attack axis
surprise was valued over supporting fire
the main effort was concentrated against enemy weak points
The assault force was usually given a detailed battle order by their commander. The shock force was broken down into sub-units with each one assigned a specific task.
Most attacks were undertaken in darkness to impede the technological advantages of US fire-support and mobility.
The power raid assault force usually included two elements.
An attack force which was further subdivided into three offensive elements (breach, shock and reserve) and two supporting elements (fire support and porters).
An ambush force whose mission was to destroy relief columns. In many cases the ambush element was larger and had the primary mission.
The breach group was usually composed of sappers armed with explosives and B-40 rockets. They began to surreptitiously clear and mark paths through the enemy wire and minefields before the attack started. Their mission was to get the shock group through the enemy mine and wire belt.
If the breach group was discovered before it had time to clear paths through enemy obstacles, all support weapons would cover it until the breaching mission was accomplished. After paths were cleared through the enemy defensive belt, the breach group would lead the charge forward and assist in destroying specified targets.
Sappers of the breach group usually had two missions;
Prepare openings in the barbed-wire and mine fields for the main assault units
Blow up specified targets inside the enemy base.
In many situations, the firing of sapper demolitions, placed on important targets within the enemy perimeter, signaled the initiation of the shock assault.
The shock group was the main assault force and usually included eighty to ninety percent of the total force. This element would attack from at least two different directions, with the main assault party attacking down the lane cleared through the defensive barriers by the sappers. If no lane through the enemy barrier was cleared, the shock force would have to clear it's own.
The shock force would advance quickly, firing and throwing grenades and satchel charges on the run. After the enemy defensive perimeter was penetrated, sub-units of the shock group would peel off in all directions, attacking pre-designated targets with demolitions and direct fire.
Shortly before the shock element launched its attack, a reserve element might launch a diversionary attack and then withdraw to its reserve position. That reserve element was used to exploit enemy weak points or to reinforce success, it was never supposed to be used to attack a part of the enemy line that was too strong for the shock troops to break into. Frequently the reserve force was used as a rearguard to protect other withdrawing assault elements.
The fire support element included all direct and indirect fire weapons such as, mortars, rockets, recoilless rifles, and heavy machine guns. These weapons were used to suppress enemy reaction, interdict movement toward the breakthrough area and to destroy point targets. A small part of the fire support element was always detailed to act as a diversionary force by drawing attention to itself and away from the main breakthrough area.
The main effort of the supporting fire was directed against point targets in the enemy camp, including machine guns, mortar emplacements, command posts, communications and ammunition dumps. The NVA/VC did not use their supporting weapons to 'soften up' their objective area since preparatory fires sacrificed surprise and they valued surprise more than the suppressive effects of prolonged bombardment. This is why most NVA/VC fire support did not actually begin until just before the shock element went in.
The other supporting element consisted of carrying parties charged with clearing the battlefield. This unit was composed of support personnel, as well as locally impressed civilians. They often went into action whilst the battle was still raging.
The attack would reach it's climax as the shock unit violently drove home its assault. Every man and weapon was dedicated to making this element succeed. Yet, the NVA/VC commander was prepared to withdraw the shock element and his whole force, if any change in the battle situation convinced him that he was risking failure or annihilation.
Although NVA/VC conventional assaults usually followed the same maneuvre rules as power raids and used similar tactics, there was a distinct difference. Conventional assaults were usually undertaken to hold objectives for a longer period of time. Conventional assaults were usually very similar to allied assault methods and frequently incorporated a complex scheme of preparatory fires which was almost studiously avoided in the power raid.