On 31 March, the 1st Cavalry Division took control of the 26th Marine Regiment, signaling the start of Pegasus, a fifteen-day air assault operation that ended the battle of Khe Sanh. The 1st Cavalry Division, along with the 1st Marine Regiment ad South Vietnamese 3 Airborne Task Force, began a push form Ca Lu, located east of Khe Sanh, to reopen Route 9 and relieve the pressure on Khe Sanh. The siege, in effect, was over.
The base plan of Operation Pegasus called for the 1st Marine Regiment, with two battalions to attack west toward Khe Sanh while the 1st Cavalry Division air assaulted onto the high ground on either side of Route 9 and moved constantly west toward the base. On D plus 1 and D plus 2, all elements would continue to attack west toward Khe Sanh. Then on the following day the 2d Brigade of the 1st Cavalry Division would land three battalions southwest of Khe Sanh and attack northwest. The 26th Marine Regiment, holding Khe Sanh would attack south to secure Hill 471. The linkup was planned for the end of the seventh day.
Fire support involved a multitude of units, requiring detailed planning and coordination for the two phases of the operation - reconnaissance and attack. The objective of the reconnaissance phase was the destruction of the enemy antiaircraft resources between Ca Lu and Khe Sanh and the selection of the landing zones for use by the advancing airmobile assault forces. The 1st squadron, 9th Air Cavalry, assumed this mission and was supported by an abundance and artillery. Additional artillery was moved onto the area during the reconnaissance phase and automatically came under the control of a forward division artillery fire direction center located at Landing Zone Stud and manned by personnel of the 1st Battalion, 30th Artillery. The additional artillery included one Marine 4.2 inch mortar battery at Ca Lu and two 105mm batteries (one Marine and one Army) at the Rockpile. On 25 March an 8 inch battery and a 105 battery moved from Quang Tri to Ca Lu and Stud respectively. This move brought the total to 15 firing batteries available to support the 1st Squadron, 9th Air Cavalry, in its reconnaissance. All batteries in the area began answering calls for fire form the 1st Squadron, 9th Cavalry, on D minus 6 and commenced attacking planned targets that night. Prior coordination between the 3rd Marine Division: the 108th Artillery Group (included the 175ís of the 2/94th at Carroll and the Rockpile); and the 1st Battalion, 13th Marines (Artillery), insured that all available target information would be in the hands of the forward fire direction center and lateral communication would be established. Throughout this phase, air and artillery fire destroyed enemy automatic weapon, mortars, and troop positions.
The attack phase consisted of the preparation of landing zones, suppression for enemy fires, and on-call support of committed ground forces. For the attack phase ten 105mm howitzer batteries, four 155mm howitzer batteries on 8-inch howitzer battery, and on 4.2-inch mortar battery joined the already overwhelming artillery force. Each cavalry brigade had reinforcing fire from a medium battery, and the 1st Marine Regiment could count on support from two 105mm batteries, one 155mm battery, and one 4.2-inch battery. The additional heavy battery with the mission of general support of the 1st Air Cavalry Division moved from Camp Evans to LZ Stud. Thirty-one firing batteries supported the relief of Khe Sanh ---- the largest array of artillery ever to support a single operation in Vietnam to that time.
Counter battery fire contributed significantly to the success of Operation Pegasus. For some time, North Vietnamese forces has been able to shell Khe Sanh at will with 152mm and 130mm artillery plus rockets and mortars positioned to he southwest and northwest of the base. When the 1st Cavalry Division Artillery came within range of the enemy guns, rapid and massive counter battery fire achieved superiority. From that point enemy artillery ceased to be a serious deterrent to maneuver.
On 6 April at 1350, six days after Operation Pegasus had begun the initial relief of Khe Sanh took place. A lead company of the South Vietnamese 3rd Airborne Task Force airlifted into Khe Sanh and linked up with the South Vietnamese 37th Rangers. Two days later the 2nd Battalion, 7th Cavalry, had completed its sweep along Route 9 and the official relief took place. The command post of the 3 Brigade, 1st Cavalry, airlifted to the base at 0800 and became its new landlord. By the evening of 8 April, all elements of the task force were in position on the Khe Sanh plateau. The North Vietnamese 304th Division faced entrapment and destruction as a great vise closed about the enemy daily. American and South Vietnamese units soon uncovered grisly evidence of how badly the North Vietnamese had been beaten. They found hundreds of North Vietnamese bodies in shallow graves and hundreds more that lay where they had fallen. The allies destroyed of captured 557 individual weapons, 207 crew served weapons and to antiaircraft pieces. In addition they confiscated 17 vehicles ranging from PT76 tanks to motor scooter, tons of ammunition and food, and numerous radios and items of individual equipment. The mountain of abandon enemy stores indicated either that Pegasus had caught the enemy flat footed or that the remnants of the enemy divisions had been unable to cart off their equipment and supplies.
On the morning of 14 April, Pegasus officially ended. The operation was successful, Rote 9 opened, the enemy routed, and the base itself relieved. The North Vietnamese lost 1,304 killed and 21 captured. The battle of Khe Sanh established that, with sufficient firepower, an encircled position could be successfully held and the enemy devastated.
Statistics for the Defense of Khe Sanh
U.S. & Allied Casualties
730 Americans Killed in Action
2,642 Americans Wounded in Action
7 Americans Missing in Action
229 South Vietnamese ARVN Killed in Action
436 South Vietnamese ARVN Wounded in Action