Militarily, the mining and the air interdiction campaign had made a serious inroad on North Vietnam’s ability to continue the prosecution of its conventional invasion of South Vietnam by cutting off most of North Vietnam’s economic and military assistance from China and the Soviet Union. Air interdiction by tactical aircraft, including those from carriers, had reduced the enemy’s overland imports from 160,000 tons to 30,000 tons per month. The mining of the North Vietnamese ports had cut seaborne imports from 250,000 tons per month to practically nothing. Unable to replace losses incurred during the fighting in the south, the North Vietnamese attack began to lose momentum after the capture of Quang Tri City.
The JCS, on the recommendation of the U.S. Navy’s Commander, Mine Force, had made the decision to employ only one type of influence mine — the magnetic. This was to facilitate later clearance operations. The Hague Convention of 1907 required that belligerents neutralize their minefields after hostilities cease. Planning for Operation “End Sweep,” the name of the operation that would neutralize the minefields in North Vietnam, had begun well before the agreements reached by the Paris peace talks. Subsequently, U.S. intelligence had reported that the mining of Haiphong was having serious effects on the North Vietnamese economy and their ability to wage war. The U.S. negotiating team, under Henry Kissinger, had proposed removal of the mines as a bargaining point to obtain the release of the U.S. prisoners of war.
LINEBACKER II
Determined to apply whatever military force was necessary to convince the leadership in Hanoi that an end to the war in Southeast Asia was going to be in their best interests, President Nixon initiated Operation Linebacker II. This, for the first time, unleashed virtually unlimited air power against North Vietnamese industrial and military targets in the Hanoi-Haiphong area. Strategic Air Command B-52 bombers, carrying full payloads of conventional bombs, were the principal striking force, escorted by U.S. Air Force and Navy fighters for protection against MiGs, and supported by tactical aircraft from the Seventh Fleet and Thai bases for flak suppression and electronic countermeasures.
The “Christmas Bombing,” as it came to be known, commenced on 18 December 1972 and continued around the clock, day and night, for twelve days. At that point the North Vietnamese sued for an immediate truce to arrange a cease-fire and agreed to negotiations to end the war. The United States had achieved a victory against Hanoi, yet not without costs. Fifteen B-52s were shot down by enemy fire. The SAC B-52 force was approaching the limit of its acceptable loss rate at the time Hanoi urgently appealed for a truce. The Seventh Fleet was heavily involved in Linebacker II and the Christmas bombings through the carrier aircraft of Task Force 77. By the eighteenth, seven carriers were in the western Pacific. From the flag bridge of the Oklahoma City I had the unique opportunity to watch six Task Force 77 carriers turn into the wind in a line abreast, stretching almost across the Gulf of Tonkin as they launched aircraft in the assaults on Hanoi.
The negotiators, meeting in France, signed the Paris Accords in January 1973. On the surface, the agreement seemed to provide both sides with legitimate reasons to conclude that the cease-fire was satisfactory to all the belligerents: In Vietnam the fighting would cease; for the United States, its military forces deployed in-theater would come home; the American POWs in North Vietnamese prison camps would be repatriated; and the U.S.-laid mines in Haiphong Harbor would be swept by mine countermeasure forces to neutralize the waterways and open the ports. The task of sweeping the mines to assure the safe passage of the approaches to the port areas of Haiphong and the other tributaries in North Vietnam fell to the Seventh Fleet. In anticipation of this requirement, Mine Countermeasures Force, Seventh Fleet, was activated on 24 November 1972 to plan and carry out the minesweeping operation and was designated as Task Force 78. On 28 January 1973, the cease-fire went into effect in North and South Vietnam in compliance with the provisions of the Paris Accords.
OPERATION END SWEEP
Airborne Mine Countermeasures Squadron 1, comprising CH-53M Sea Stallion helicopters, immediately commenced its deployment from the Norfolk Naval Base to the Gulf of Tonkin. This squadron had been stood up two years earlier at the Norfolk Naval Air Station, when I was deputy commander in chief, U.S. Atlantic Fleet. So I was quite familiar with the minesweeping techniques involved and the tactics that would be employed by these helicopters. Each of the CH-53M aircraft, the largest operational helicopters in the U.S. inventory, would tow a sled in the water, with the helicopter flying at an altitude of between three and six hundred feet. The sled carried a powerful electrical generator, which fed electromagnetic pulses to a wire, called the “tail,” trailing from the sled into the water. These electronic pulses would be programed to detonate the electromagnetic arming and explosive devices in the mines that had been laid by the TF 77 aircraft in the Haiphong estuary. Fuel to run the generators was carried in the helicopters and flowed from the helicopter tanks in a hose attached to the towline from the helicopter to the sled. At the completion of a mine countermeasures sortie, usually determined by fuel availability, the helicopter would return to a landing ship dock (LSD) and drop the towline in the water. The helicopter would then land on the LSD. A small craft would pick up the towline to the sled and retrieve it, pulling the sled, with the towline and the two extended antennas, into the LSD’s flooded dock for postflight inspection and setup for the next sortie. Meanwhile, the helicopter would be refueled and launched to pick up the towline and start on another sweep pattern.
The helicopters had been transported from NAS Norfolk, Virginia, by C-5 transport, two CH-53s per aircraft with the rotor heads and the rotors removed. The Sea Stallions were flown to Subic Bay, Philippines, where they were offloaded at the Cubi Point Naval Air Station, their rotors were reassembled, the aircraft was checked out mechanically, and they were then flown to the helicopter carrier Inchon. When the entire component of squadron aircraft had been delivered, reassembled, and embarked on board the helicopter carrier, the Mine Countermeasures Force departed Subic Bay to rendezvous with the Seventh Fleet flagship off the coast of North Vietnam east of Haiphong.
Preparation for Operation End Sweep had commenced in September 1972, when Commander, Mine Force, U.S. Atlantic Fleet reported to me as Commander, Task Force 78, the Mine Countermeasures Force in the U.S. Seventh Fleet in the western Pacific. The TF 78 staff had been bolstered by the inclusion of the Navy’s most knowledgeable and experienced mine warfare experts, including Capt. Felix S. Vecchione, who was virtually unmatched in his knowledge and experience of the technical development and tactical application of naval mines.
Task Force 78 was officially activated in November 1972, and there was ample opportunity to collect assets for the operation and deploy them to the Seventh Fleet before 23 January 1973, when the “agreement on ending the war and restoring the peace in Vietnam” was signed in Paris. In accordance with the agreement, preparations for the return of the prisoners of war (Operation Homecoming) were made, the removal of mines from Haiphong Harbor (Operation End Sweep) was scheduled to commence within a month, and combat air operations over both North and South Vietnam were ended.
The day after the cease-fire was signed, the main elements of Task Force 78 deployed from Subic Bay to the Haiphong area. These forces included four ocean minesweepers (MSO), the helicopter carrier Inchon, and four amphibious ships, including two with docking capabilities to handle the minesweeping sleds towed by the CH-53Ms. During the six months of Operation End Sweep, ten ocean minesweepers, nine amphibious ships, six fleet tugs, three salvage ships, and nineteen destroyers operated in Task Force 78 in the vicinity of Haiphong.