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Marine and U. S. Army air observers ventured north of the DMZ-an area previously accessible to them only at grave risk-to assist in adjusting fire and providing battle damage assessments. The damage to the NVA defenses was so great that even the vulnerable O-Is operated over the area for the rest of Operation Thor without sustaining any casualties, or indeed, receiving any hits.

The air observers reported that the Cap Mui Lay sector was a fortified area. Most villages consisted of a group of dug-in huts, with only their roofs above ground, connected by a series of trenches. Although rice was visible in the open in many villages, there was no evidence of farming activity, indicating that the enemy shipped in rice from other areas. Few personnel sightings occurred, but light antiaircraft fire came from several of the fortified villages. Fire missions directed against these villages often caused secondary explosions, indicating the storage of ammunition or fuel. There was every sign that the Cap Mui Lay sector was a military garrison area and that its villages were actually supply dumps or troop staging points.

During the final days of Operation Thor, III MAF artillery continued to pump an average of about 4,000 rounds per day into the target area, while naval gunfire added another 3,300 rounds per day. Air strikes totaled a further 2,400 tons of bombs, with 1st Marine Aircraft Wing crews flying 256 attack sorties. On the afternoon of 7 July, VMCJ-1 flew the final photo reconnaissance mission of Operation Thor. The next morning, artillery units began withdrawing from the forward positions, while air and naval units resumed normal operations.

Operation Thor expended enormous quantities of ordnance. Attack aircraft delivered 3,207 tons of bombs, while B-52s dropped an additional 5,156 tons. III MAF artillery units fired 23,187 rounds of 155mm, 175mm, and 8-inch ammunition. Ships of the Seventh Fleet accounted for 19,022 rounds of 5-inch, 6-inch, and 8-inch naval gunfire. The human cost of this massive application of firepower was low. On the ground, one soldier was slightly wounded by NVA counterfire, while Marine, Navy, and Air Force aviation units flew more than 2,000 sorties with the loss of three aircraft destroyed and one crewman killed in action. Marine aviation units and artillery units sustained no losses.

In assessing the damage to the North Vietnamese in their former sanctuary area, the after-action report filed by XXIV Corps stated that "severe damage was inflicted upon the enemy." The report cited as evidence "the minimal and ineffective hostile fire from the Cap Mui Lay Sector in the thirty days subsequent to THOR and the continued ability of our observation aircraft to operate over that area."39

Damage assessments included the destruction of 789 antiaircraft positions containing 63 weapons; 179 artillery positions containing 19 guns; l43 bunkers; 9 surface-to-air missile sites; and numerous trucks, sampans, structures, storage areas, and other miscellaneous targets. Pilots and observers noted 624 secondary explosions and fires. Unconfirmed reports of North Vietnamese killed totaled 125, but without the opportunity to send ground troops to investigate the area, the actual figure could not be determined. MACV noted:

Finally, there may well have been one contribution that could not then or perhaps at any later time be measured with assurance: If the enemy had intended using the CM1S [Cap Mui Lay Sector] as a staging point for staging a major infiltration program into the South, that possibility had been preempted. And preemption has always been one purpose of interdiction.40

Following the completion of Operation Thor, Lieutenant General Richard E. Stilwell, commanding the newly redesignated XXIV Corps, pressed for continued overflight of the Cap Mui Lay sector by air observers and forward air controllers to sustain the success of the operation by daily engagement of recovering NVA targets, but this was not done. On 1 November 1968, all questions of how best to exploit the gains of Operation Thor became academic when, by order of President Johnson, all offensive operations against North Vietnam and the DMZ, including air strikes, artillery missions, and naval gunfire missions, were discontinued, except as necessary to retaliate to Communist attacks. Thus, the sanctuary was restored.41 Fire Base Tactics

By July 1968 with the imminent abandonment of the Khe Sanh base, the 3d Marine Division had instituted a mobile concept of operations patterned to a large extent upon the 1st Air Cavalry. While not completely abandoning the Dyemarker strong points, Major General Raymond G. Davis, who assumed command of the 3d Marine Division in May, had each of them manned with as small a force as possible, usually not above company strength. Starting with the Task Force Hotel operations in western Quang Tri, the 3d Division began a series of wide-flung heli-

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