The Micro-Arc Light was executed in the same manner as the Mini except smaller amounts of ordnance were used and the block was cut down to 500 by 500 meters. Any aircraft on station would suffice, preferably ones armed with 12 to 16 500-pounders. Artillery fire was reduced to 30 rounds from the 175mm guns and 100 mixed rounds from Lieutenant Colonel Hennelly's battalion. The advantage of the Micro was that it could be put into effect within 10 minutes while it took roughly 45 minutes to plan and execute the Mini. On an average night, three to four Minis and six to eight Micros were executed, usually to the south and southeast of the base; both were extremely effective.(160) The massive firepower supporting the Marines would have been almost useless had they not known where and when to employ it. The 26th Marines intelligence section was responsible for this facet of the operation and these people had more than a passing knowledge of the enemy's past strategy. At Dien Bien Phu and Con Thien, the Communists had followed a fairly predictable pattern--not unlike the classic siege of the 18th Century. There were three distinct phases involved in this type of campaign: arrival on the scene and encirclement of the garrison, construction of siege works and support facilities, T-ing the sapheads and final assault. After investing the base, the North Vietnamese first established numerous forward logistic bases within a few thousand meters of the base. Under the cover of darkness, the enemy soldiers dug a series of shallow trenches, interlaced with supply bunkers, leading from these points toward the American positions. The first trenches began to appear at Khe Sanh around 23 February and the heaviest concentration was to the south and southeast. Once in close, the main trenches branched off into ones which paralleled the Marines lines; these secondary trenches, which from the air looked like long fingers reaching greedily toward the base, were the ones from which the NVA assault troops intended to attack.(161) At first, the defenders tried to prevent the enemy from moving in too close to the base. The routes into the valley were saturated; artillery H&I fire and frequent air strikes were employed but such tactics only tended to slow down the enemy and force him to bypass certain routes--they did not stop him. Constant, massed artillery would have effectively blocked infiltration but that alternative was, from a logistics standpoint, impossible. The S-2 personnel recommended that the best way to counter the enemy was to allow the North Vietnamese to close and pursue their siege tactics and then, to borrow a phrase used by General "Chesty" Puller (then a colonel) on 28 November 1950 when his regiment was surrounded near the Chosin Reservoir in Korea, "that simplifies our problem of finding these people and killing them."(162)