Category Archives: history

AN HM-12 CH-53D tows a MK 105 sled during Operation End Sweep

On 8 May 1972, as part of Operation Pocket Money (itself a part of Operation Rolling Thunder), 3 A-6 Intruders (from VMA(AW)-224) and 6 A-7 Corsairs (from VA-22 and VA-94) launched from the USS Coral Sea (CV-43) to deploy mines within the vicinity of Haiphong Harbor in North Vietnam.

An illustration of the Southeast Asia are of Operations.

The A-6 flight led by the CAG (Commander, Carrier Air Wing), Commander Roger Sheets, was composed of USMC aircraft from VMA-224 and headed for the inner channel. The A-7Es, led by Commander Len Giuliani and made up of aircraft from VA-94 and VA-22, were designated to mine the outer segment of the channel. Each aircraft carried four MK 52-2 mines. Captain William Carr, USMC, the bombardier navigator in the lead plane established the critical attack azimuth and timed the mine releases. The first mine was dropped at 090859H and the last of the field of 36 mines at 090901H.

A-6A Intruder from VMA(AW)-224.

Twelve mines were placed in the inner segment and the remaining 24 in the outer segment. All MK 52-2 mines were set with 72-hour arming delays, thus permitting merchant ships time for departure or a change in destination consistent with the President’s public warning. It was the beginning of a mining campaign that planted over 11,000 MK 36 type destructor and 108 special MK 52-2 mines over the next eight months. It is considered to have played a significant role in bringing about an eventual peace arrangement, particularly since it so hampered the enemy’s ability to continue receiving war supplies.

Operation Rolling Thunder itself served as a way to get the North Vietnamese back to the negotiating table in Paris. Prior to Operation Pocket Money, the US Navy planning offices had studied minesweeping operations off Haiphong but the assets to conduct minesweeping were not properly maintained.  However some sweeping had taken place off Saigon in preparation for a non-combatant evacuation. Most of the minesweeping assets in theatre were devoted to Operation Market Time in South Vietnam. Most of the minesweeping equipment dated from the Korean War era. In 1970 the US Navy had made a decision to place more emphasis of minesweeping from helicopters due to the increasing cost of MSO (ocean-going minesweepers).

There were about 8 months between the time that CINCPAC (Commander-In-Chief Pacific) had received orders to begin minesweeping and the time the task force remained on-station to conduct sweeping operations. This allowed time for development of equipment, tactics and training.

Between the dates of May 9-11 of 1972, as assessment of problems was conducted. There were no oceanographic charts of the operational area off Haiphong, there was no data to give accurate predictions of equipment losses that could occur during operations, there was a lack of specialized personnel and training (both in the officer and enlisted ranks).

In 1972 mine countermeasures for both the Atlantic and Pacific Fleets were combined was under one type commander – Commander Mine Warfare Force, based in Charleston, South Carolina. What follows is a list of operational resources that were in this organization:

-One Mobile Mine Countermeasures Command (MOMCOM). This was the command structure to provide worldwide airborne and other support of minesweeping operations.

-Three Mine Flotillas. Each Flotilla was composed of a number of MSOs.

-One Helicopter minesweeping squadron. Helicopter Minesweeping Squadron 12 (HM-12) was the airborne component to the task force.

-One squadron of minesweeping boats (MSB and MSL).

-One Mine Force Support Group. They were responsible for training and equipping personnel for minesweeping operations.

HM-12 was equipped with 12 CH-53Ds. 2 of the helos were in use at the Naval Coastal Systems Laboratory. The CH-53Ds were on loan from the USMC and were configured with towing strong points required for mine countermeasures towing.

HM-12 patch

These helos towed the MK-103 gear for sweeping moored mines, the MK-104 gear for acoustic mines and MK-105 hydrofoil for sweeping magnetic mines.

Schematic drawing of the MK-105 minesweeping sled, showing the major components of the device.

Other airborne assets that didn’t necessarily belong to MOMCOM but were tasked to them were USAF C-5A Galaxies that were used to airlift the CH-53Ds to the theatre.

An example of an MSO used during Operation End Sweep, the USS Constant (MSO-427).

Most of the surface born mine sweeping assets were the 172 ocean minesweeper (MSOs). By 1972 most of these ships were 13 to 19 years of age with 5 in the Western Pacific, 17 on the west coast and 11 on the east coast another 17 were in the Naval Reserve Forces and 13 were in an inactive status.  14 of these MSOs had received new engines to improve their useful lives and decrease the maintenance necessary for effective operation. Other vessels were the eleven 144 foot coastal minesweepers and nineteen 57-foot minesweeping boats.

The minefields off Haiphong were too shallow for sweeping operations by any of these types of vessels. However sensors towed by these vessels like the AN\SQO-14 sonar gave these vessels the ability to map the bottom of the ocean at sufficient resolution to detect mines. The only capability these vessels had to dispose of the mines were EOD divers.

The Naval Scientific Assistance Program (NASP), provided solutions to problems of immediate concern. For example, the NASP developed simulators for use in training and automated minesweeping planning software. As a side note, the NASP expressed a concern of solar flare activity in August of 1972. NASP thought these flares caused a large number of mine detonations of Destructor mines in US minefields off North Vietnam.

There were other problems concerning preparation for Operation End Sweep. Among them being a general lack of funds for training and equipment (which admittedly was a problem throughout all US forces at the time. Problems specific to minesweeping forces detailed to Operation End Sweep were reliability problems for degaussing, sonar (AN/SQO-14), and engines on the MSOs. There was no equipment for precision navigation and mapping of minefields. There was no oceanographic data for sea floor in the vicinity of Haiphong. The was no protection for the CH-53Ds that were involved in minesweeping.

HM-12 conducted training from May to November 1972 off of Charleston, South Carolina. The CH-53Ds operated from an LPD (Landing Platform Dock) and crews learned how to rig the minesweeping equipment to the helo. LCVPs (Land Craft Vehicle and Personnel or “Higgins Boat”) carried the MK-105 sleds to the waiting hovering helos. The sleds were then attached to the towing strong points on the aircraft.

Training of both surface and air forces for Operation End Sweep as done off of Panama City, Florida. Most of these tests were to test the accuracy of the Raydist. EOD teams also conducted training with surface minesweeping forces.

On 6 November 1972, Task Force 78 deployed to Subic Bay in the Philippines. Forces kept a low profile on base because TF-78 was being used as a bargaining chip in the Paris peace talks. The CH-53Ds were deployed to Subic via USAF C-5 Galaxy.

In January 1973 the Paris Peace Treaty was about to be signed and TF-78 forces ramped up training. Crews from HMM-165 trained with HM-12 aboard the USS Ogden and USS Dubuque. MSOs USS Fortify, USS Force, USS Impervious and USS Engage began sweeping the anchorage for the TF, some approaches to Haiphong. Operations were being monitored by the Soviet Intelligence Collection Ship, Protractor.

By 26 February, airborne units from HM-12 were ready to be deployed aboard ships. HM-12 was divided into 4 detachments, each aboard 4 ships in the task group. Dets Alpha and Bravo embarked aboard the USS Ogden, USS Dubuque, and USS New Orleans. Dets Charlie and Delta embarked aboard the USS Inchon (LPD-12) and USS Cleveland (LPH-7).

General planning for sweeping operations in Haiphong actually started in 1972 as part of general contigency planning on the part of JCS. By mid-1972 however clearing the mines in Haiphong become a diplomatic issue at the Paris Peace Talks. The initial planning for End Sweep were known as Formation Sentry I and Formation Sentry II. These plans differed from End Sweep through the numbers and assets to be used. The Sentry plans were completed by 1972 but held ready by CINCPACFLT (Commander-In-Chief Pacific Fleet).

Imputes to expand Formation Sentry I into Formation II occurred because of what became known as the Warrington incident in June and July 1972. While conducting naval bombardment 10 to 20 miles northeast of Dong Hoi, the USS Warrington was damaged by an underwater explosion that was determined to have been possibly caused by a Destructor mine laid as a result of an aircraft navigation error.

This incident led the JCS (Joint Chiefs of Staff) to determine that MSOs were particularly suited to ocean-sweeping operations in this area and prompted a danger zone to be established in the area. The area was never swept because a Naval Oceanographic team was trying to survey the area and was fired on by shore batteries. The area was never cleared (except for the self-destruction of the mine). The Warrington incident did bring increased interest of Minesweeping to the JCS and the appropriate planning offices were notified.

Ships of Task Force 78 at anchor in the Gulf of Tonkin.

By 24 November 1972 Task Force 78 (TF-78) was activated. TF-78 consisted of the following:

-Surface Support Group (Task Group 78.0) consisting of LPH and LPD types to serve as helicopter platforms and supporting ships such as the fleet ocean tug and salvage ship. Five helicopter platforms were available plus a flagship-maintenance platform. An amphibious squadron commander led the Surface Support Group.

-Mobile Mine Countermeasures Group (Task Group 78.1) the airborne group, contained the 4 airborne units (A,B,C,D), the special minesweeper Washtenaw County and various other units. Commander TG-78.1 was in overall command of sweeping in coastal and port areas.

-Surface Mine Countermeasures Group (Task Group 78.2) consisted of the 10 MSOs assigned to End Sweep. TG-78.2 acted as control ships for the helo minesweeping operations.

-Advanced Base Mine Countermeasures Group (Task Group 78.3) was stationed at Subic Bay. This group provided maintenance, repair and supply to the entire task group; trained Marines in MCM and coordinated installation of sweeping kits and the Swept Mine Locator Camera System on the helicopters. Civilian technical representative from the various contractors were also part of this group.

-Contingency Mine Countermeasures Group (Task Group 78.4) was activated later and primarily responsible for sweeping the inland waterways in North Vietnam. They were also primarily responsible for supervising North Vietnamese sweep personnel.

-Salvage Group (Task Group 78.5) was responsible for finding and disposing buried mines in the Haiphong Channel.

On 27 January, MSOs began sweeping the anchorages of Haiphong where the main ship in TF-78 would be operating. On the 29th, the Paris Peace Agreement was formally signed by representatives from the United States, The Republic of Vietnam, The Democratic Republic of Vietnam and the National Liberation Front.

By May of 1972, the largest mine countermeasures force the world had ever seen, up to that time, had assembled and was ready for action.

In the next part of this series we’ll get into the minesweeping equipment used in Operation End Sweep and the operation itself.

This was my first attempt to tell some “non-aviation” history that I felt needed to be told.  If I’ve missed something or said something in error as usual you feedback is more than welcome.