The Tet Offensive (Tết Mậu Thân)
Operation PEGASUS and the End of Khe Sanh
Westmoreland began ordering plans for the relief of Khe Sanh as soon as the battle began, but the plans had to be postponed due to the sudden onset of the Tet Offensive. Finally, in early March, Gen. John J. Tolson, commander of the 1st Air Cavalry Division, revealed his plan for Operation PEGASUS. Tolson would use elements of the 1st Air Cavalry Division, the 3rd Marine Division, and the 3rd ARVN Airborne Task Force to reopen Route 9 and relieve the base.
Initial resistance from the NVA during Operation PEGASUS was minimal. The Marines at Khe Sanh began patrolling farther and farther from the base as the units from PEGASUS progressed. The NVA began offering heavy resistance after the first few days of the operation, but by 8 April parts of the 1st Air Cavalry Division had reached the base and Route 9 was declared fully open by 11 April. Operation PEGASUS was officially declared complete on 15 April and the 1st Marines replaced the 26th Marines at the Khe Sanh base. American casualties during PEGASUS consisted of 92 killed, 667 wounded, and 5 missing. The ARVN suffered 33 killed and 187 wounded while estimates for NVA casualties reached over 1,000.
The final number of casualties on both sides during the Battle of Khe Sanh remains an unresolved topic. The final listing of Marine casualties at Khe Sanh was 205 killed and 1,662 wounded. However this number is misleading in the sense that it covers 1 November 1967 to 30 March 1968 rather than just the seventy-seven days of the siege. 1 November represents the commencement of Operation SCOTLAND, which was the last of several operations conducted by the Marines to protect the Khe Sanh base and conduct patrols in the area. Thus the number of casualties listed goes beyond those suffered during the siege in the sense that it counts those suffered up to two and a half months before the siege began. On the other hand, it does not take all of the casualties into consideration in the sense that it does not include the number of Marine reinforcements who were killed in the air while trying to enter Khe Sanh or those who were killed while evacuating. The number of NVA dead found in the area was listed at 1,602, but the total estimated by American intelligence ranged anywhere from 10,000–15,000.
Ironically, it was only two months after the Khe Sanh base had successfully been relived by Operation PEGASUS that it was closed. Westmoreland declared that he would keep the base open, however he left Vietnam on 11 June 1968 to become Army Chief of Staff and was replaced General Creighton Abrams as commander of MACV. Abrams soon decided to abandon the base saying that the NVA had changed tactics in the area and that the Marines had enough men and helicopters for mobile operations, making the base at Khe Sanh unnecessary. Many in the Marine Corps questioned if it was ever necessary to occupy Khe Sanh, but it was a moot point by 6 July 1968 as the base had been officially destroyed and the area evacuated.