A map of North Vietnam with the shaded areas representing mined areas.
It was never the intention of the Nixon Administration to make sweeping mines in the South China Sea a political issue. Nevertheless, on 16 May 1972, the Washington Evening Star quoted Nixon as saying “the mines will go when the POWs (Prisoners of War) are free.” SECSTATE Kissinger saw that eventually minesweeping could be used to help bring our POWs home because the DRV (Democratic Republic of Vietnam) were the one that initially raised the mine sweeping issue in connection with handing over the POWs. By 15 December, 1972 the White House told SECDEF (Secretary of Defense) that the JCS (Joint Chiefs of Staff) should review it’s minesweeping plans for North Vietnam. On 20 December, the JCS responded to the Whitehouse and SECDEF by saying clearing the mines posed an “undue risk to Naval personnel.” However, by that time the peace processes was faltering and Operation Linebacker II commenced, resulting in an increased mining of the waters off North Vietnam. Eventually the DRV did return to the peace table and on 27 January DRV signed a “Mine Clearing Protocol” as part of the so-called Paris Peace Deal.
The most important issues directly related to OES (Operation End Sweep) in the protocol were:
Article 3: consult immediately on relevant factors and agree upon the earliest possible target date for the completion of work.
Article 4: set a meeting between Naval representative from the US and DRV “At a later date. (these meeting actually began before the protocol was signed).” During this time the US Navy gave some rudimentary technical details on how the Destructor mines worked.
Article 5: Specified that DRV should actively participate in clearing/sweeping inland waterways using equipment and training that was given to them by the US.
By 5 February a “Haiphong Clearing Committee” had met to discuss the technical details of minesweeping the Haiphong area. These meetings took place on TF-78 Task Force 78) ships.
On February 6th, MSOs entered and swept the anchorage where the larger ships of TF-78 would stay. USS Impervious swept the area and marked with the path with buoys. Sweeping in the vicinity of the anchorage continued south of Grand Norway Island on the 7th.
Sweeping the northern ports over the southern ports and inland waterways but the problem was the large between in the minefields the DRV had charted and the minefields that the US Navy charted. The sweep plan stated only areas where known mines were and/or had self-destructed or sterilized would be swept. By 7 February the LPH and LPDs arrived at the anchorage while other airborne units continued training at Subic Bay. Another DRV point of contention was the insistence on the Navy giving the DRV towing gear and earth moving equipment to dig-up and move buried mines. However, at the time, the US was unwilling to allow this.
The first merchant ship departed Haiphong around the 7th, before sweeping of area had even begun. These shallow draft ships were empty (having already unloaded military equipment before the mining began) and used US supplied minefield charts to make the run into the South China Sea at high tide. Even before US Navy sweeping operations began, the NVN (North Vietnamese Navy) used Soviet supplied “closed loop” mine sweeping gear to sweep portions of the port of Haiphong.
On 21 February, airborne mine seeping assets arrived on-scene. The first airborne sweep by an HM-12 CH-53D (with a UH-1E in the lead) occurred on 27 February. Meanwhile on 23-25 February, Raydist equipment was installed ashore at Do Son, Cat Bai and Dinh Vu. These were transported ashore by CH-46s from HMM-165. A fourth Raydist was installed on board the fleet tug, USS Tawasa (ATF-92).
Early in the morning on the 28th, sweeping operations stopped because the POWs were not being returned per agreement. OES was being used as the “carrot” to get the DRV to return the POWs but the DRV wanted mine sweeping equipment for sweeping the inland waterways on their own. Agreement to this was reached on 5th March and operations resumed on the 6th.
Magnetic Orange Pipe
Northern ports and villages were swept for the next 6 weeks. Airborne unit Alfa swept the Haiphong area using the MK-105 sweeping gear. Unit Bravo, using the MOP swept the Cua Cam area. On a side note, airborne units, Charlie and Delta never trained with the MK-105 gear.
On 9 March at 1240 local, the first and only mine swept, a MK-52, detonated behind in the vicinity of a MK-105 being towed behind a CH-53D. Most of the deployed mines by the time of OES had already self-sterilized.
On the 13th, the Soviet merchantman, Zayson transited the Haiphong channel inbound.
On the 17th, the USS Enhance, had an engine room fire. Enhance was anchored in the outer approach to Passe Henriette. USS Safeguard assisted and brought the Enhance under tow. That same day an HM-12 CH-53D lost it’s tail rotor and crashed. All the crew were recovered. After this all CH-53s (throughout the US Navy and USMC) were grounded and inspected. On March 25 a MK-105 undertow collided with a “civilian” 12ft wooden skiff. There were no injures but there was some minor damage to the –105.
An HM-12 CH-53D Super Stallion.
Another CH-53S was lost on 2 April due to a tail rotor failure. It splashed down in Haiphong harbor and the crew was recovered. As a result, a more extensive inspection of all OES CH-53s occurred. Pitch change rod end assemblies were replaced and gearbox inspections were increased to every 10 flight hours. Flights resumed on 6 April.
The USS Washtenaw County seen transiting the main channel in Haiphong harbor.
By 14 April the USS Washentaw County transited Haiphong’s main shipping channel to demonstrate is navigability but by the 17, this was cut short again because the DRV failed to meet the agreed to cease-fire in Laos and Cambodia. On the 24th, elements of TF-78 departed the area for Subic Bay.
On 24, April the USS Force had and engine fire and sunk about 770 miles east of Guam, on it’s way to OES. The crew was recovered by a Norwegian merchant ship.
Taking TF-78 off the line allowed for TF-78 to undertake a reassessment of OES. The Navy estimated that most of the mines had self sterilized by the first week of May. As of the 16 April, in the Haiphong area 3 days each of sweeping at Cua Cam and Lach Tray channels and 2 additional transits by Washtenaw County in the main shipping channel were all that remained to be done. In the Hon Gai and Cam Pha, 6 and 2 days, respectively, of airborne screening remained. Remaining operations would be conducted as a check sweep because all mines completed their self-sterilization period of 6 months. There was also an assessment of equipment that the Navy had given to the DRV.
Operations resumed on 20 June and an agreement was also in place to give the DRV more equipment for sweeping the inland waterways, which, by now, they were going to do on their own. Most of the check sweeping was done around Lach Huyen and on the 26 mine sweeping in the north by Haiphong was finished. On 28 June operations shifted to Vinh. Alfa swept near Hon La and Bravo swept Quang Khe.
On 4 July the fatality of OES occurred when a flight deck crewman on the USS Ogden caught in the closing stern door of a CH-53 that was taking off.
Finally, Operation End Sweep, wound down by 20 July 1973. The closing dispute between the Navy and the DRV was over bulldozers. The DRV wouldn’t accept the condition of the TD-6 bulldozers. The TD-6s were thought, by the DRV, to be in poor material condition. There was a final meeting on 18 July 1973 to resolve this issue but nothing ever came of it.
Elements of TF-78 left the DRV for Subic Bay and on 27 July 1973 TF-78 was dissolved 6 months to the day it was formed.
In total, the Haiphong area accounted for 70% of the tow hours. The 3 northern port areas required 87% of the tow hours. Generally the sweeping was carried out to a 95% certainty that no live mines remained.
Here’s a summary of End Sweep units:
CH-53Ds: 37 aircraft
13 USN HM-12
24 USMC HMM-463 and HMM-165
Ocean Minesweepers (MSOs): 10
Mine Flotilla 1 Western Pacific
Naval Reserve Training Force ships, based in Hawaii
Washtenaw County (MSS-2)
I was trying to find out exactly who the only fatality was. I was unable to find out. If anyone does know, please let me know. I’d like to dedicate these posts to his sacrifice.
For more information on the different elements of OES see the following:
The Naval Historical Society’s page on OES.
Navsource.org has a few more pics of the vessel involved.
102 Minesweepers has some good stuff.
Eagle One has some good info on the history of airborne minesweeping.
Finally, some more history of airborne mine countermeasures here.
2 books provide context and further information:
Hartman’s “Weapons That Wait: Mine Warfare in the US Navy” and the Naval Historical Society’s “Operation End Sweep: A History of Minesweeping Operations in North Vietnam.”