During the Rolling Thunder bombing campaign (1965-1968), the U.S. Navy's carrier air squadrons released thousands of mines along the enemy's key supply routes in the "panhandle" area of North Vietnam. The object of the operation was to make vehicular and other movement around ferry crossing sites, railway and highway bridges, storage areas, truck parks, and fuel dumps difficult if not prohibitive for the enemy. Carrier attack aircraft also "seeded" inland waterways and roads used by the Communists to transport munitions into Laos and South Vietnam. The weapons used were Mark 36 Destructors, which contained 500 pounds of explosives and detonated when trucks, tanks, or other metal objects disturbed their magnetic fields. Neither the Navy's mining effort nor the overall bombing campaign stopped the flow of munitions to the fighting front but they forced the enemy to devote scarce resources to defense of his supply line.
Another mining operation, which the Navy carried out during 1972 and early 1973, had an even greater impact on the war. Early on the morning of 8 May 1972, aircraft carrier Coral Sea (CVA 43) launched three Marine A-6 Intruders and six Navy A-7 Corsair attack planes toward the coast of North Vietnam. Shortly afterward, the naval aircraft laid strings of thirty-six 1,000-pound Mark 52 mines in the water approaches to Haiphong, through which most of North Vietnam's imported war material and all of its fuel supply passed. During succeeding months, other carrier aircraft dropped thousands of mines and 500-pound, Mark 36 Destructors in the seaways of North Vietnam's secondary ports and "reseeded" the Haiphong approaches.
For the remainder of 1972, twenty-seven Sino-Soviet bloc merchant ships chose to remain immobile in Haiphong rather than risk a transit of the mined waters. The mining campaign, along with U.S. air attacks on North Vietnam's supply lines ashore, helped cut short the enemy's "Easter Offensive" in South Vietnam. Eventually, the mining operation and the Linebacker bombing campaign induced the North Vietnamese to negotiate an end to the war.
On 27 January 1973, American and North Vietnamese officials signed a protocol to the Paris agreement that called for the United States to neutralize the mines that the Navy had dropped in North Vietnam's coastal and inland waterways.
On 28 January, following months of preparation, Rear Admiral Brian McCauley's Mine Countermeasures Force (Task Force 78), of the Seventh Fleet, deployed from Subic Bay in the Philippines to Haiphong. To coordinate actions, on 5 February Commander Task Force 78 met in the city with his North Vietnamese opposite, Colonel Hoang Huu Thai. Operation End Sweep began the next day, when ocean minesweepers Engage (MSO 433), Force (MSO 445), Fortify (MSO 446), and Impervious (MSO 449) swept waters off the coast near Haiphong. Guided missile frigate Worden (DLG 18) and destroyerEpperson (DD 719) stood by in case the North Vietnamese tried to interfere with the effort. Later that month, amphibious ships New Orleans (LPH 11), Dubuque (LPD 8), Ogden (LPD 5), Cleveland (LPD 7), and Inchon (LPH 12) joined the task force. On board the newly arriving ships were 31 CH-53 Sea Stallion helicopters from the Navy's Helicopter Mine Countermeasures Squadron 12 and from Marine helicopter squadrons HMM-165 and HMH-463. The Sea Stallions towed minesweeping sleds and other devices. During the six months of Operation End Sweep, 10 ocean minesweepers, 9 amphibious ships, 6 fleet tugs, 3 salvage ships, and 19 destroyer types operated in Task Force 78.
The helicopters swept the main shipping channel to Haiphong on 27 February and the ports of Hon Gai and Cam Pha on 17 March. In early April, Commander Task Force 78 deployed to the formerly mined waters MSS 2, a decommissioned LST filled with buffer material and crewed by volunteers. The ship carried out eight passages of the Haiphong channel to make sure no mines remained active in the vital waterway. Elsewhere in North Vietnam, U.S. Navy technical personnel prepared 50 North Vietnamese sailors to conduct their own minesweeping operations. While this was taking place, a number of U.S. C-130 transport aircraft delivered minesweeping gear to Cat Bi Airfield outside the city. Until 17 April, the Navy task force continued its mission. Then, because Hanoi failed to carry out its obligations under the Paris agreement, Washington ordered a suspension of minesweeping operations. End Sweep resumed on 18 June when American leaders were persuaded that the North Vietnamese would once again act in good faith. Shortly afterward, Admiral McCauley notified the North Vietnamese that the ports of Haiphong, Hon Gai, and Cam Pha were free from the threat of American-laid mines. Next, Task Force 78 concentrated on the coastal areas off Vinh. Finally, on 18 July 1973, McCauley led his flotilla out to sea, officially ending Operation End Sweep.
Reproduced with permission from: Tucker, Spencer C., ed. Encyclopedia of the Vietnam War: A Political, Social, and Military History. Santa Barbara, CA: ABC-CLIO, 1998.