the 514th Battalion allowed their opponents to come within before opening fire. Immediately, the South Vietnamese infantrymen were forced to hug the ground. During the next five hours, they managed to launch three major assaults but failed to break the VC's line of defense. By 09:30, the last of Dam's reserve companies had been airlifted into Tan Hiep, about two hours late because American aircrews were prevented from landing their CH-21 helicopters, known as "flying bananas" for their shape, in the heavy fog that covered Tan Hiep Airfield most of the morning. With the ground attacks in the north and south bogged down, Dam decided to stretch out the defending VC units by attacking the east and the west. Dam asked Vann, who was circling the battlefield aboard an L-19 reconnaissance aircraft, to reconnoiter possible landing zones on the east and west sides of Ap Bac where additional reinforcements could be inserted to launch their attacks. In response, Vann asked his pilot to make low passes over the trees which covered Ap Bac. Although he could not see any VC positions, Vann knew there was a well-fortified position at the south end of the hamlet, due to the impact of the VC's firepower on the Civil Guards since the battle's inception. As Vann's L-19 aircraft flew over the western tree line, the VC watched from their foxholes but held their fire because they knew the aircraft was trying to draw fire in order to mark their positions. Although Vann was suspicious, he decided it was a better landing zone because the area was tranquil despite the heavy fighting elsewhere. Vann then ordered his pilot to make contact with the other L-19 that was leading the ten CH-21s with the first South Vietnamese reserve company from Tan Hiep. Vann relayed a message to the command pilot of the ten CH-21 helicopters, which were being escorted by a group of five recently deployed UH-1 Huey gunships, armed with 7.62mm machine guns and 2.75-inch rockets and instructed him to land the reserve companies about from the western and southern tree lines that covered Ap Bac in order to minimize the effectiveness of the VC's .30 caliber machine guns. However, in the early phases of the war, command relationships between US military units were not well-established, and American aircrews tended to disregard the instructions of advisors, especially Vann, who was regarded as domineering. Instead