This article was originally published in the March 1974 issue of Proceedings magazine by Rear Admiral Brian McCauley, U. S. Navy
Western strategists of every stripe had grown hoarse calling for the mining of Haiphong Harbor and, at last, it was done. Now, with the ceasefire signed, the mines had to be retrieved or destroyed and, as surface ships of Task Force 58 trailed a sweeping helicopter into Haiphong on 17 June 1973, the end of “End Sweep”—a tedious, lengthy, and totally unglamorous job—was in sight.
Operation End Sweep had its beginning in early 1972. Commander Mine Warfare Force as the major, and almost only, source of mining expertise was asked to assist in the planning of the mine fields to be laid by the Seventh Fleet in North Vietnamese waters. From the beginning, the possibility of U. S. forces having to sweep the mines was a factor which influenced the types of mines used, their settings, and to a lesser degree their locations. As a result, when it came time to sweep, we knew everything about the mines and had purposely planted mines which could be swept easily and effectively by our mine countermeasures forces. The mines in the North Vietnamese fields were of the type actuated by either magnetic or acoustic influences, or by a combination of the two. Sensitivity was varied in both types. The vast majority of the mines were programmed to self-destruct and the remainder to go inert after a given time. Thus, even as the mines were dropped, the process of mine removal had been started.
Actual preparation for the mine sweeping operation began in July 1972 when it first became apparent that mine sweeping would, as expected, be an important part of the peace negotiations. By this time, the Navy’s Airborne Mine Countermeasures (AMCM) program was underway. Helicopter Mine Countermeasure Squadron 12 (HM-12) was operational with 13 Sikorsky Sea Stallions (CH-53). Basic training with towed sweep gear was underway. Initial deployments of units of four helicopters by C-5 aircraft to the Mediterranean and by cross country to the west coast had been made. In October, a mine field simulating those off the Haiphong Channel was planted off Panama City, Florida. Together with the Naval Coastal Systems Laboratory (NCSL), a detachment of HM-12, controlled by Commander Mobile Mine Countermeasures Command, began developing tactics, equipment, and experience in how best to counter the mines.
In the year or so since the helo minesweepers had been activated, a great deal had been accomplished. In the pre-End Sweep exercises, considerable knowledge was acquired on countering the simulators which used the detection devices of the actual mines laid in North Vietnam. This was accomplished under controlled conditions, but it provided a basis to start the future operation. There was and is much more to be learned. The mine countermeasures used in the operation were developed or improved upon in this period. The basic magnetic mine countermeasures device was the MK-105 sled manufactured by the Edo Corporation. Towed at speeds to 25 knots, this foil-supported generator streams a standard magnetic tail astern. In addition, NCSL developed a 33-foot iron pipe which was permed with a DC coil to give it an increased magnetic signature. This was filled with styrofoam to keep it afloat and towed at speeds of 10 to 25 knots. Painted orange, it was commonly known as the MOP (magnetic orange pipe). Against certain settings, three MOPs were towed in tandem. Noise makers could be towed independently or astern of either the MK-105 sled or the MOP.
While the operational training was proceeding, members of the CoMineWarFor staff were visiting Washington and Hawaii to firm up requirements, force levels, organizational structure, chain of command, and the myriad of details involved in establishing for the first time a major task force to support a combined surface and airborne sweep in North Vietnamese waters. After much discussion and many changes, the size of the force was fixed.
The airborne sweep was carried out by four Airborne Mine Countermeasures (AMCM) sweeping units. Two of these were made up of the 13 Navy HM-12 helos augmented by three Marine CH-S3 helos provided by HMM-16s. These two units towed the MK-105 magnetic sled, the MK-104 and the AMK-2 G acoustic devices, the MOP or the triple MOP (three in tandem). To support the sweeping helos and other administrative helos were an LPH and two LPDs. Each AMCM unit operated from an LPD. The well deck and open stern ramp were necessary to launch the MK-105 magnetic sled. The LPH provided maintenance support to the helicopters and was the task force commander’s flagship. The two additional AMCM units were made up of 15 Marine CH-S3 helicopters from HMH-463. As the Marines had had no AMCM training prior to joining Task Force 78, their training was limited to the MOP and the acoustic devices. These two units operated from an LPH and an LPD. As there was no requirement for the well deck (to launch the MK-105), an LPH was used as an AMCM launch platform. The LPH also provided maintenance for the Marine helicopters. Other helos, which provided control platforms as well as transportation ashore and between ships, were divided between the two LPHs according to maintenance spaces and work shop availability.
The surface mine sweeping force was made up of ten ocean minesweepers (MSOS). These were used principally in the deep water approaches and as helicopter control ships. In addition, a surface support force was made up of two destroyers, two fleet tugs (later reduced to one), a submarine rescue ship, an LST for MSO support, and a specially configured LST to transit the Haiphong channel after sweeping had been completed in order to demonstrate confidence in the thoroughness of the sweep.
The Commander in Chief Pacific Fleet made the decision that Commander Mine Warfare Force was to be the task force commander. This was unique in that a type commander is seldom an operational commander. Type commander functions for both Fleets were left to the residual staff in Charleston. The operational chain of command was from the JCS through CincPac, CinCPacFlt, ComSeventhFlt to CTF 78. This proved cumbersome at times because most vital decisions were made in Washington, often with a short time fuze.
Task Force 78 was made up of the following Task Groups:
• CTG 78.o Commander Amphibious Squadron One was responsible for all major surface movement and the seaborne logistic support of the Task Force.
•CTG 78.1 Commander Mobile Mine Countermeasures Command directed operational control of all sweeping helicopters through AMCM units on each of the helocapable amphibious ships. In addition, he had overall control of all coastal harbor and port mine sweeping, both surface and air.
•CTG 78.2 Commander Mine Flotilla One maintained operational and support control for the ocean minesweepers.
•CTG 78.3 Supervised and provided base support from Subic Bay, P.I.
•CTG 78.4 A command established later in the operation which was responsible for all MCM and other activities in inland waterways.
• A diving and salvage expert, responsible for any contingencies and for mine hunting if necessary.
The order to deploy was received on 4 November 1972. For all but a few planners this was the first indication that the MCM force would actually deploy. Within two days Helicopter Mine Countermeasures Squadron Twelve (HM-12) was ready to deploy from Norfolk, Virginia with 13 helicopters and about 450 men. From Charleston, S.C. more than 100 officers and men from Mine Warfare Force and Mobile Mine Countermeasures Command, together with all necessary mine sweeping gear, were ready in an equally short time. Ten C-5s were used to transport the east coast MCM force to Subic Bay. Soon after, three ocean minesweepers sailed from Long Beach and two Reserve minesweepers were readied to sail from Pearl Harbor. The crews of the latter two were augmented by volunteers from the active MSOs in Charleston. These minesweepers, together with five Guam-based ships, completed the surface mine sweeping force.
After arrival in the Philippines, the peace negotiations in Paris collapsed. That left the deployed east coast units in Subic with no indication of when the MCM operation would be undertaken. By this time it was apparent to all that the mine sweeping task was directly related to the progress of the negotiations. The period was used to identify Seventh Fleet ships, equipment, and personnel needed to round out the task force. Both CinCPacFlt and ComSeventhFlt were most effective in understanding and implementing the priority which had been assigned to Operation End Sweep. At this time, and understandably so, it was often difficult to convince the operators that the conflict was nearly over and that mine sweeping would then have as high a priority as current (December 1972) operations. Conferences were held with ComSeventhFlt, the Marine helo commanders, the amphibious commanders, and various support commanders for the purpose of establishing roles, missions, and lines of authority.
Finally, on 27 January 1973, the ceasefire agreement was signed in Paris. The Protocol on mine sweeping became the Bible of Operation End Sweep. The Protocol was much broader and more demanding than expected.
Among other things it stated:
•The United States will clear all the mines it has placed in the territorial waters, ports, harbors and waterways of the Democratic Republic of Vietnam (D.R.V.). This … shall be accomplished by rendering the mines harmless through removal, permanent deactivation or destruction.
• Mines shall, on request of the D.R.V., be removed or destroyed in the indicated areas; and wherever their removal or destruction is impossible, mines shall be permanently deactivated and their emplacement clearly marked.
• Start, completion dates, priorities, timing and methods of sweeping would be accomplished by a mutual exchange of information.
•The United States shall be responsible for mine clearance in the inland waterways of the D.R.V. The D.R.V. shall, to the full extent of its capabilities, actively participate in the mine clearance with the means of surveying, removal, and destruction, and technical advice supplied by the United States.
The general nature of these words made them subject to any number of interpretations. And the resolution of their exact meaning was the subject of almost daily negotiations for the entire time the Task Force was in North Vietnamese waters.
The Protocol called for an initial meeting between the North Vietnamese and the United States to arrange procedures for the mine sweeping operation. After some negotiations both in Paris and through the Four Party Joint Military Committee then meeting in Saigon, it was agreed that meetings would be held alternately in Haiphong and on board a U. S. warship. On 5 February, CTF 78 flew from Saigon to Hanoi in an Air Force C-130, along with a 14-man staff. The group was flown from Hanoi to Haiphong in a Russian IL-14. The baggage and a communication jeep were taken to Haiphong in an MI-6 Russian helicopter.
Engage (MSO-433), Force (MSO-445), Fortify (MSO-446) and Impervious (MSO-449) had been sailed from Subic for the Tonkin Gulf on 27 January, coincident with the signing of the agreement. After assurance from the North Vietnamese that U. S. minesweepers would not be molested, they were ordered into North Vietnamese waters off Haiphong. Operation End Sweep actually commenced on 6 February with the four MSOs sweeping the areas in which the LPHs and LPDs were to anchor. In the meantime, the amphibious ships and Marine helos were assembling in Subic Bay. There the Marine CH-53S were modified to enable them to tow. Navy pilots from HM-12 together with personnel from the Mobile Mine Countermeasures Command commenced training the Marines to tow the MOP. The individual aircraft training was topped off by an eight-day exercise where conditions simulating the conditions expected off Haiphong were set up. Search and Rescue procedures were developed, aircraft and personnel were trained. Normal SAR procedures could not be used because of the difficulties involved in rescuing personnel from a live minefield. During the period in which the heavy ships were in Subic, the USS Worden (DLG 18) acted as flagship for CTF 78 and as an alternate site for meeting the North Vietnamese.
The first two of the AMCM units arrived in Haiphong on 23 February. This force consisted of the Navy Helicopter Squadron HM-12 augmented by three Marine CH-53S and other Marine support helos on board New Orleans (LPH-11), Dubuque (LPD-8), and Ogden (LPD-S). Actual airborne mine sweeping began on the afternoon of 27 February when two missions were flown in the Haiphong main shipping channel. That night, because of difficulties over the second pow exchange, the force was withdrawn. Within 12 hours of the withdrawal, the issues were resolved and TF 78 was ordered back into North Vietnamese waters. By this time the two Marine AMCM units had joined in Inchon (LPH-12) and Cleveland (LPD 7) and TF 78 was ready to sweep with all four AMCM units. Sweeping in the Haiphong area was resumed on 6 March. Because of difficulty with the North Vietnamese, who wanted all four units to sweep the Haiphong main channel, sweeping in the two other northern international ports of Hon Gai and Cam Pha was not started until two weeks later. From then until 17 April, all four AMCM units swept daily in Haiphong, Hon Gai, and Cam Pha. The MSOs continued to sweep in the deep water approaches to these three ports.
On 17 April, because of difficulties in Laos and Cambodia, it was decided to again withdraw the force. The period of inactivity lasted until 13 June when the Paris Joint Communique was signed. The time was used for additional training, upkeep, and liberty. It was, again, a difficult time because there was no indication when, or even if, the Task Force would go back and complete the operation. The 13 June communique was specific for the first time. It stated that the United States would resume the sweeping within five days of the signing and would complete the operation 30 days after that. It would have been possible to do this because by June all of the mines were well past their self-destruct date. There was considerable statistical evidence to ensure that the vast majority of the mines would self-destruct and that any left would be inert and totally deactivated. Because of this, all sweeping after 18 June was exploratory sweeping. This is considerably less time consuming than full sweeping.
Prior to leaving Haiphong on 17 April, the sweep in the Haiphong main channel had been completed. The demonstration ship, a modified LST (MSS-2), had made a number of runs through the channel, but not enough to declare it open. On 20 June, the remainder of the runs were completed and the North Vietnamese were handed a signed memorandum stating that the United States had completed the sweep in the Haiphong main channel. Hon Gai and Cam Pha were completed on 27 June. Plans were to systematically sweep the remainder of the coast. There remained Vinh, Quang Khe, Dong Hoi, Than Hoa, and about a dozen small fields. The North Vietnamese, however, wanted the Task Force to go directly to Vinh, Quang Khe, and a section known as the Hon La coastal area. We agreed to move the force south and commenced sweeping again. Coastal negotiation sites were shifted from Haiphong to Vinh. These areas were completed on 5 July, and again, memorandums of completion were handed to the North Vietnamese. Attempts were then made to obtain agreement to sweep the remainder of the fields. The North Vietnamese refused and the result was a stalemate which lasted until the Task Force left Vietnamese waters at the expiration of the 30 days on 18 July. Each day, U. S. negotiators would ask to sweep other areas and each day they were refused.
The inland waterways sweep was also frustrated by the North Vietnamese. The U. S. Navy had actually not expected to be charged with the mine sweeping responsibility inland. When the Protocol so dictated, a great amount of talent was put to work to devise ways and means of sweeping these rivers and channels. Both acoustic and magnetic devices were made by the Naval Coastal Systems Laboratory in Panama City, Florida. These were tested there and under field conditions in a river at Subic Bay. Non-magnetic radiocontrolled boats and motors were purchased to tow the various devices. A force of 50 two-man teams was assembled to supervise and instruct in the inland waterways. After much tedious and difficult negotiation, a school was set up near Haiphong. Here about 40 young North Vietnamese were taught how to use the various equipments, how to maintain the motors, and the fundamentals of the MK-36 destructor. When this was completed in about three weeks, the North Vietnamese said they had enough training and what they wanted was more equipment. About this time it became apparent that the D.R.V. did not want any U. S. military personnel to help them inland. As a result, the United States did no sweeping or supervising of sweeping in the inland waterways. Upon Task Force 78’s return the second time in June, all of the mines had passed their self-destruct date. To our knowledge no sweeping was done in inland waterways. Negotiations continued to the end. The North Vietnamese continually asked for additional equipment. The United States provided a reasonable amount on loan to sweep the inland waterways, but no more. The equipment was brought into Cat Bi airfield by C-130 aircraft, certainly the first U. S.operated airfield in North Vietnam.
It would be a mistake to attempt to devise general, long-standing mine warfare conclusions from the specific operational and political arena in which End Sweep was conducted. End Sweep was a unique solution to a unique problem and did not present a challenge of nearly the magnitude that can be expected in the future. The location, type, and settings of all mines were known. The vast majority of mines were the DST-36, a very sensitive magnetic or acoustic fuze placed on a 500 pound aircraft bomb. The magnetized pipe (MOP) was effective against this mine. It will not counter properly designed sophisticated mines. Much of the sweeping was done in very shallow water, often as shallow as three feet. Additionally, Operation End Sweep had the highest priority in the Pacific Fleet. It commenced with the ceasefire and, as a result, people, ships, and aircraft, which in a wartime scenario would have been otherwise occupied, were made available. The objective of the sweeping was largely accomplished prior to laying the mines when the self-destruct time was set into the fuze.
The helicopter proved ideal for the operation. With little training and minor modifications the Marine pilots and helos were taught to pull the light MOP and to be controlled either by a surface ship radar or the Raydist Precision Navigation System. Had the mines been more sophisticated, training would have been a much more complicated task. The time needed to train the Marine pilots and crews to stream and tow the more complicated MK-103 moored mine sweep gear or the MK-105 magnetic sled would have been much greater. The Marines did a magnificent job in the task assigned. The dedicated Navy mine sweeping helo squadron, however, was available to tow the more complex gear.
Flying a helicopter low and slow towing a heavy load is a most demanding task. The skill necessary to do this can only be obtained and maintained through constant practice. To have a helicopter mine sweeping force ready at all times it will be necessary to maintain specialist crews flying special aircraft. Larger and more powerful helos will in the future most certainly become more specialized. It may, for instance, be possible to devote one of the three engines of future aircraft to generating power for a magnetic tail. This will obviate the need for a complex sled carrying a sensitive turbine and generator at sea level where it is subject to a constant shower of salt water.
Operation End Sweep demonstrated that the helo, with certain limitations, is here to stay as a minesweeper. HM-12 had been commissioned two years when the operation commenced. The time had been totally devoted to mine sweeping. Four plane deployments had been made previously. When called upon, HM-12 and the Mobile Mine Countermeasures Command were able to deploy their entire force within two days and could have been sweeping anywhere in the world within four or five days after that. The mobility of the helo force, airborne in C-5s, is staggering to one who has been hampered by the slow SOA of the surface minesweeper. The helicopter in Operation End Sweep proved itself against magnetic and acoustic mines. Its speed both for transit and for towing is a tremendous asset. Because it is airborne it can safely punch through a known mine field. A surface ship to survive must approach a mine field cautiously from the side, hoping to sweep the area prior to entering. The helicopter, however, suffers from the limitations of all aircraft. It is handicapped in mine sweeping by extreme weather and darkness. Fuel-limited mission time reduces the flexibility and increases the requirement for numbers of helicopters. This is especially true when cumbersome equipment such as the MK-103 moored mine sweep gear must be streamed. Streaming and recovery may well take up half the mission time. In order to operate for any sustained period, a good maintenance facility must be provided. The LPH is ideally suited for this. Her shops, equipment, and personnel have been especially prepared for the role. The LPD was an excellent launch platform for the helicopters and MK-105 sled. It could not, however, do other than the most minor maintenance. Without adequate support, the helicopters could not have been kept flying.
The helicopter must have some sort of control and a record of where it has been. In End Sweep, both the Raydist Precision Navigation System and surface ships were used. The Raydist system requires antennae ashore or on ships in a four-point moor. Surface ship control requires a ship close to the mine field. The entire mine sweeping operation thus is vulnerable to any enemy opposition. This is a lesson we learned in Korea and it still applies. The helicopter based ashore is an attractive proposition. Almost all ports in the world have a site large enough to operate helos. Thus, in any controlled port using the Raydist or similar system, the helo could operate with a shore based control and support system.
Even with the success of the helicopter sweeping, End Sweep demonstrated again the need for surface minesweepers. The MSOs were used for sweeping and for helicopter control. In large area sweeps in deep water, their more powerful magnetic gear and their ability to sweep around the clock proved invaluable. Since the MSO has a very small magnetic signature, it proved an ideal helicopter control vessel as it could move in close to the field. Six to eight MSOs were kept on the line for the entire sweeping period. Their total support consisted of one LST, an obvious plus on the side of economy. The MSO, however, is very limited by its speed. The sweeping is done at four to seven knots and transits are made at about ten knots. It is unable to go directly into a mine field as can a helo. The MSO can sweep to much greater depths than the helo. It currently has the only useful system against a pressure mine, the mine hunting sonar. Pressure mines must be found-and then destroyed or avoided.
The forseeable future will require both helos and surface ships: the helos for rapid deployment to any part of the world; the ships for use closer to home or their bases where speed is not a handicap. Both the helicopters and the surface ship will require future development. A shift to hydrofoil or hovercraft can offset to some degree the speed limitations and vulnerability of the present surface ships. Helos should be provided with all-weather capabilities, high resolution sonar for mine hunting, and a submerged mine attack capability. More powerful helos should carry more fuel for increased mission time. The complex moored gear can be simplified to reduce streaming and recovery time. The current helicopter has no capability against deep moored mines. The MSO is also limited in its capability against these mines. A larger ship with higher transit speeds will have to be provided if this threat is to be met.
Perhaps the most important lesson learned in End Sweep was one that we must continually relearn. Mine sweeping of any sort is difficult, tedious, lengthy, and and we were totally devoid of glamour. Even if with the “cooperation” of the D.R.V.and knowledge of types, location, setting, and expiration dates of the mines, we were compelled to devote a large force and exercise great caution to ensure that the seas and the ports were clear. Without this information the task would have been infinitely more difficult.
The most obvious conclusion one reaches in reviewing Operation End Sweep is the effectiveness, relative ease of laying, and the economy of the coastal mine campaign. It was an impressive sight on flying over Haiphong in the early days of End Sweep to see all 26 merchant ships at anchor behind the mine field. None had moved since May when the first mines where dropped. Few aircraft were lost during their emplacement. The effectiveness of this demonstrates once again the vulnerability of a country which has little or no mine sweeping capability to mining. The North Vietnamese ocean shipping was paralyzed until we arrived with the technical knowledge to clear their main channels. Thus, the mining campaign provided a potent lever to U.S. negotiators both before and after the Peace Agreement. When he commended the Navy for outstanding performance during End Sweep, Admiral T.H. Moorer, Chairmain of the Joint Cheifs of Staff, stated: “The efforts of the Navy in Operation End Sweep contributed significantly to the timely release of U.S. prinosers of war, and that is to the attainment of the nation’s objectives in Southeast Asia.”
U. S. ports on both coasts are particularly susceptible to covert or overt mining. Because of lack of glamour and parochial support there has
been a tendency to let the mine warfare community force wither away for lack of funds. We must not allow this to in the future.
Rarely will anyone in today’s Navy argue against the effectiveness of mine warfare nor our vulnerability as a nation to its use by other powers. Yet the practical demise of the Mine Force in the U.S. Navy is already planned—a victim of other more sophisticated, higher priority programs. We ahve relegated the Mine Force to a miniscule size and are even now considering some assets for other roles. There is no new surface minesweeper on the boards and none is now contemplated when the wooden-hulled MSOs—newest age 15—finally expire.
The Mine Force has been compared to the Phoenix, that mythical bird which rises out of its own ashes to live and fly again. With the loss of experienced and interested officers and the erosion of its few remaining assets with no replacement, the ashes may already be too few and too scattered to the Phoenix to rise and conduct another End Sweep.