While the Marines were learning to adapt their technology to the guerrilla war environment, the enemy was applying his ingenuity in attempts to frustrate the American and South Vietnamese helicopter operations. The Viet Cong quickly learned to capitalize on the presence of large crowds of civilians who sometimes gathered near helicopter landing zones to watch the strange aircraft. One such incident occurred in June when Communist soldiers mingled with a crowd and delivered fire on helicopters which were lifting elements of the 21st ARVN Division. Two aircraft were hit by enemy fire although the damage was not extensive enough to force them to land. The Marines, who refused to return fire with their individual weapons unless the Viet Cong could be separated from the civilian populace, found no effective method of countering this tactic. Later in June, the Marines of HMM-362 encountered another tactic when they found that hundreds of upright bamboo stakes had been prepositioned in the intended landing zone. The perpendicular spikes, each four or five feet high, not only prevented the helicopters from landing but also made it impossible to disembark the ARVN troops while hovering. Fortunately, the abundance of landing zones in the delta region tended to make this particular tactic ineffective.[5-E] [5-E] The German army had used a similar technique (upright poles) to obstruct landing zones against U.S. paratroops at Normandy during World War II. (Taylor, _Swords and Plowshares_, p. 80.) On 20 July, HMM-362 added a new dimension to the counterguerrilla capabilities of the South Vietnamese forces when it executed the first night helicopter assault of the war. The mission, which began at 0415 at Soc Trang, involved lifting three waves of ARVN troops into an objective on the Plain of Reeds, about 40 miles southwest of Ben Tre. The ARVN force intended to encircle a suspected Viet Cong village before dawn and then attack it at daybreak. The Marine portion of the airlift was completed 10 minutes before daylight after which the Army’s 57th Helicopter Company joined the operation. Although the night troop lift was executed without incident, Lieutenant Colonel Clapp attributed its success at least partially to the near perfect conditions. The moonlight, reflected from the flat, flooded rice paddies, had aided the Marine pilots in the tricky operation.[5-19]