The Second Battle of Quảng Trị (; also called Operation Lam Sơn 72) was a battle in the Easter Offensive beginning on 28 June 1972 and lasting 81 days until 16 September 1972, when the South Vietnamese army (ARVN) defeated the North Vietnamese army (PAVN), leading to the ARVN recapturing Quảng Trị Province south of the Thạch Hãn River. This was the longest and fiercest battle in the Vietnam War, where South Vietnam played the main role while the U.S. only provided fire support for its ally.
Background During the initial phase of the Easter Offensive, the PAVN passed the Demilitarized Zone and quickly captured Quảng Trị in the First Battle of Quảng Trị (30 March – 2 May 1972) and overran all of Quảng Trị Province. The ARVN regrouped forming a defensive line along the Mỹ Chánh River northwest of Huế and, together with U.S. support, the Battle of the Mỹ Chánh Line halted the PAVN offensive by 26 June.
Planning On 14 June, I Corps commander, Lieutenant general Ngô Quang Trưởng briefed President Nguyễn Văn Thiệu and Joint General Staff chairman General Cao Văn Viên on his planned counterattack to retake Quảng Trị Province from the PAVN. Thiệu was not convinced, preferring a smaller-scale operation. Trưởng finally convinced Thiệu, emphasizing that such an effort would be possible "employing the superior firepower of our American ally." Thiệu finally approved the concept and Operation Lam Sơn 72 was launched on 28 June.
The probing attacks in June tested PAVN strength and allowed for the establishment of advance positions ahead of the launch of Trưởng's operation to recapture Quảng Trị Province. The operational plan called for the Airborne (RVNAD) and Marine (RVNMC) Divisions to advance abreast to the northwest to the Thạch Hãn River. The Airborne Division would deploy to the west from the foothills to Highway 1, while the Marine Division would deploy to the east from Highway 1 to the coast. Quảng Trị City would be in the Airborne Division's operational area, but the plan called for the city to be bypassed so as to concentrate on the destruction of PAVN forces. As a diversion the U.S. 9th Marine Amphibious Brigade (9th MAB) would conduct a feint amphibious assault against the mouth of the Thạch Hãn River in Cửa Việt.
Battle
On the morning of 27 June the 9th MAB launched their amphibious feint against Cửa Việt, reversing course when 7 km from shore.
On 28 June the South Vietnamese advance began and quickly ran into strong PAVN resistance and helicopter assaults were launched to land troops behind PAVN positions. On 29 June, following preparatory airstrikes the VNMC 1st and 4th Battalions were landed by U.S. Marine helicopter squadrons HMM-164 and HMM-165 near the Wunder Beach area. That day a 20th Tactical Air Support Squadron OV-10 Bronco that was operating as a forward air controller in support of the VNMC was hit by an SA-7 missile and crashed into the sea, killing its pilot, Captain Steven L. Bennett, who would be posthumously awarded the Medal of Honor. By the end of June the Allies had killed 1,515 PAVN, destroyed 18 armored vehicles and the Marines had taken 15 PAVN prisoners.
By 7 July the Airborne Division had reached the southern outskirts of Quảng Trị City, but then Thiệu intervened in the operation. Trưởng had planned to bypass the city and push on quickly to the Thạch Hãn River, thereby isolating any PAVN defenders. Thiệu, however, now demanded that Quảng Trị be taken immediately, seeing the city as "a symbol and a challenge" to his authority.
The ARVN assault bogged down in the outskirts and the PAVN, apprised of the plans for the offensive, moved the 304th and 308th Divisions to the west to avoid the U.S. airpower that was about to be unleashed upon Quảng Trị.
The defense of the Quảng Trị Citadel () was left to PAVN replacement units and militia. One participant recalled: "The new recruits came in at dusk. They were dead by dawn... No one had time to check where they were from, or who was their commander. Others described the defense as a "senseless sacrifice" and referred to Quảng Trị as "Hamburger City". Nevertheless, the PAVN units stationed within the citadel were well dug in, had the advantage of terrain and mass artillery supports. An early ARVN victory was denied, and the fighting continue unabated.
By 10 July, the forward units of the VNMC 1st, 3rd, 5th, 7th and 8th Battalions were on a line that ran generally from the bend in Route 555 as it turned west toward Quảng Trị, eastward to the coast. With the Airborne Division stalled on the outskirts of the city, VNMC commander General Bùi Thế Lân was reluctant to expose an unprotected flank as his division continued northward. To break the impasse, Lân decided to move one battalion by helicopter across the Vĩnh Định River to a position just northeast of the city while two battalions would assault PAVN positions from east to west. The mission of the Marines was to block Route 560 and to prevent the PAVN from resupplying their forces in the city itself.
On 11 July, following preparatory B-52 strikes, the VNMC 1st Battalion was deployed by HMM-164 and HMM-165 helicopters to two landing zones 2 km northeast of the city to cut Route 560, the main PAVN supply line. This move would force the PAVN to reinforce and resupply across the Thạch Hãn River, making them vulnerable to air strikes. The helicopters were met by heavy anti-aircraft fire with one CH-53 being hit by an SA-7 and crashing with two U.S. Marine crewmen and 45 South Vietnamese Marines killed. Two CH-46s were shot down and their crews rescued by helicopters from the U.S. Army Troop F, 4th Cavalry while another 25 helicopters were damaged. Despite these loses the South Vietnamese Marines deployed successfully and consolidated their positions with air and artillery support against the opposing PAVN 48th Regiment, 320B Division. The Marines killed 126 PAVN, captured six, secured large quantities of material, and flanked the PAVN position. Fighting continued in the area for three days before the PAVN retreated to the west. During the same period the 7th Battalion overran an armored regiment's command post. A ban on U.S. airstrikes within the city was instituted on 15 July because Thiệu wanted Quảng Trị recaptured by his army without American assistance. However an attack of the ARVN against the PAVN on 3 August bogged down, so Thiệu was forced to lift restrictions on U.S. airstrikes within Quảng Trị. The Republic of Vietnam Air Force (RVNAF) received some of the CBU-55 fuel-air devices from the U.S. in time to try them against the PAVN in this battle.
By 20 July the Marine Division had consolidated its position north of Quảng Trị City, while the Airborne continued trying to break in. On 22 July the Marines launched a three battalion operation against PAVN supply lines south of the Thạch Hãn River. The 5th Battalion would be landed by HMM-164 helicopters 4 km north of the city, while the other two battalions, supported by tanks would attack north, the combined force would then move southeast. The helicopter landing proceeded smoothly, while the ground assault met heavy resistance and could only break through PAVN defenses with air and artillery support. After two days the Marines had killed 133 PAVN and destroyed three tanks.
On 27 July, the Marine Division was ordered to relieve the Airborne units as the lead element in the battle. Progress was slow, consisting of vicious house-to-house fighting and incessant artillery barrages by both sides. During July, the ARVN claimed the PAVN lost more than 1,880 dead, 51 armored vehicles captured or destroyed and seven antiaircraft guns, four artillery pieces, a 20-ton ammunition dump and 1,200 individual weapons captured. During July, U.S. aircraft flew 5,461 tactical sorties and 2,054 B-52 strikes and operated five aircraft carriers to support the counteroffensive.
As August began, most of Quảng Trị remained in PAVN hands. The territory north and west of the Thạch Hãn River, particularly around Ái Tử Combat Base, was dotted with PAVN artillery units which maintained a seemingly ceaseless artillery and mortar barrage on the South Vietnamese. The Marine brigades were well placed to deny PAVN resupply and to make a final lunge into the heart of the city, the Citadel, but were held off by the well-concealed defenders. PAVN fire and the congestion of friendly units in the area severely hampered maneuver by the Marines. 147th Brigade, operating northeast of Quảng Trị, began receiving heavy pressure from the PAVN, but had thwarted several attempts by the numerically superior PAVN to reopen Route 560 northeast of the city. The Marines' supply blockade began to take its toll on the PAVN's ammunition stockpiles. All PAVN supplies making their way into the city had to be ferried across the Thạch Hãn River. To the south, the 258th Brigade, with four maneuver battalions under its operational control, was in heavy house-to-house fighting around the Citadel. The 3rd Battalion attacked from the northeast, with the 6th and 9th Battalions closing in from the southwest. Each day, the 258th Brigade moved slowly forward, tightening its grasp on the PAVN forces still in the Citadel. This slow progress made Lân realize that he would have to reinforce his maneuver forces if they were to overpower the three PAVN regiments holding the Citadel. Lân continued to keep the 369th Brigade in division reserve. On 22 August, after an artillery barrage on the 8th Battalion a sizable PAVN force led by tanks attempted to break out from the Citadel. The Marines, surprised at such an action, quickly rallied and drove the PAVN back into the Citadel. During the remainder of the month, the PAVN increased the number of night attacks in an effort to break through the Marine lines.
As September began, Marine units had been in constant street fighting inside the city for 35 days under some of the heaviest enemy artillery shelling since the invasion in March. The forward maneuver battalions had been under daily counterattacks by units of the 308th Division. In the city, the 1st, 3rd, 5th, 6th and 8th Battalions attacked through the rubble to reach the Citadel and the Highway 1 bridge over the Thạch Hãn River. On 5 September the PAVN attacked the 5th Battalion's command post at dusk and were met by artillery fire and directing air strikes. At 21:30 the PAVN withdrew in confusion having left behind more than 50 individual and crew-served weapons.
A battalion from the 147th Brigade had taken up positions at the An Tiêm Bridge where Route 560 crossed the Vĩnh Định River. All PAVN supply and infiltration routes and lines of communication to the north were effectively blocked. The PAVN were feeling the bite of supply and ammunition shortages. On 8 September, the three battalions of the 1st Ranger Group relieved the 147th Brigade of its blocking mission north of the city. Lân now had two brigades he could commit in the pincer movement which would begin the all-out assault on the city. The 258th Brigade continued its attack along the southern front with four battalions while the 147th Brigade attacked from the northeast with the 3rd and 7th Battalions. Trưởng and Lân also requested an amphibious diversion by the U.S. Seventh Fleet to draw the enemy away from the Marines attacking the Citadel. The U.S. amphibious forces agreed to carry out the feint, except for an actual landing.