[Illustration: A-6 Intruder, under TPQ control, provides precision bombing around Khe Sanh despite poor weather. (USMC Photo A422000)]
[Illustration: B-52 Stratofortresses flew strikes daily in support of the 26th Marines. (Photo courtesy USAF)]
In addition to its accuracy, the TPQ system was extremely flexible. A strike could be programmed and executed within 10 or 12 minutes utilizing any available aircraft. Most of the missions were at night when it was inefficient and dangerous to conduct dive-bombing strikes. As a matter of routine, two Marine and three Air Force flights were scheduled every hour unless an emergency developed. On 18 February, ASRT-B set a new squadron record for a single 24-hour period by controlling aircraft which delivered 486 tons of ordnance on 105 separate targets. After that, the record was approached frequently but never broken. During the siege, ASRT-B controlled 4,989 TPQs in support of the 26th Marines.(150)
Beginning on 20 February, ASRT-B also assisted with supply drops whenever the Khe Sanh MATCU was inoperable. Normally, the controllers could have guided the transport pilots to an exact release point but, at Khe Sanh, the C-130s had to fly directly over the station and the TPQ-10 would break lock.[57](151) Therefore, the ASRT personnel used the same technique as the MATCU controllers and called a "Mark" when the Hercules was over the eastern threshold and the pilots completed the runs with Doppler navigation and stop watches. The only problem was that, when the ASRT conducted supply drops, it was drawn away from the primary mission of handling TPQs.(152)
While air support was vital to the defense of the base, Colonel Lownds felt that his artillery played an equally important role. When the fighting first broke out, the colonel surmised that the side which managed to keep its artillery intact would win the battle. The Marine artillery emerged almost unscathed. Many incoming rounds landed within the battery positions, however, very few actually hit the gun pits and throughout the operation only three artillery pieces at the base were destroyed; one was a 155mm howitzer parked alongside the loading ramp awaiting airlift to Dong Ha.[58] Generally the pieces, were tucked away inside heavily sandbagged revetments and, while the crews were often showered with fragments, it would have taken a direct hit, squarely on top of the weapon, to knock out a howitzer. Fortunately for the Marine gunners, the North Vietnamese scored only one such a hit which led the regimental commander to the conclusion: "Either they were amazingly inaccurate or we were amazingly lucky."(153)