Stephen Thomas


Warship International Magazine

Number 2, 1974 Issue

Special Reprint of

First Generation SEAL Support Craft
Stephen L. Thomas
Boat Support Unit One
December 1968 - April 1971
May/Nov 1969
Apr/Oct 1970

Once in Vietnam I asked a SEAL officer just what, to his mind, constituted the perfect SEAL operation. He replied that a perfect operation was one wherein he and his men had gotten into the target area, carried out their mission, and then gotten back out again without casualties. "And," he added, " I am back in the Nha Be Officers' Club before Charlie finds out I've ever been anywhere else.
Authors Biography: Stephen Thomas was born Charleston, SC, 30 January 1940. Attended Charleston public schools and flunked out of MIT in January 1958 after one ....

It is obvious from this that stealth plays a vital part in SEAL team operations. And necessarily so. Hostile forces in the vicinity almost always outnumber the SEAL squad or platoon assigned to a particular mission, so that stealth, surprise, better training and superior equipment are vital to the SEAL team.

One of the two converted LCM-6 HSSC. Note the armor protection abreast the engine room and around the conning position. Note also the cut-down ramp and duck-boarding, and the shield and screens for the .50 cal. machine guns amidships. (USN photo) sthomas1.jpg (66078 bytes)

Part of the stealth surprise and equipment required for SEAL operations in the Republic of Vietnam was provided by the men of Mobile Support Team Two, whose specially configured boats provided transportation, fire support and communications support for the SEALS, and whose presence on occasion turned potential disaster into tactical victory. This article is the story of the first six of these specialized SEAL support craft, of which it was once said that they were the only boats to be seen on the rivers at night, except for Viet Cong junks. Indeed, even the Viet Cong felt great respect for the MST-2 boats. Documents were captured in which VC units were warned not to engage these boats when it was not possible to do so at an advantage, unless taken under fire first.

When it was first decided to commit the SEALs to the struggle against the Viet Cong and their North Vietnamese allies, suitable boats to support the operations did not exist, nor were the other means of insertion available suitable for the half-land, half-water environment of the Mekong Delta region. The necessity for an undetected approach to the objective area ruled out helicopters and existing types of river patrol boats, while the few more or less suitable small craft lacked one or more essential qualities -- load carrying capacity, endurance, ability to serve as heavy weapons or communications platforms. Approach by land was clearly ruled out in an area where roads, if they exist, served merely to connect canals, and can be considered as being under constant surveillance by hostile forces or sympathizers. For obvious reasons, insertion by parachute was out of the question. Boats it had to be, and in Coronado, in Little Creek and in Washington wheels began to turn. Design studies were undertaken which ultimately resulted in the highly successful LSSC and MSSC, light and medium SEAL support craft respectively. To meet immediate requirements it was decided to convert existing naval boats, and to purchase and modify suitable civilian small boats as interim SEAL support craft.

At first, three classed of boats were considered necessary: heavy and medium units to act primarily as communications and fire support platforms, to provide long-haul mobility and to serve secondarily as insertion/extraction craft; and light units to serve as the primary insertion/extraction craft, and to provide close-in fire support in emergency situations. For the latter role a well-known civilian runabout, the Boston whaler, was selected. Its shallow draft, great speed and low silhouette were to keep it in active service long after the specially-designed LSSC arrived in Vietnam. It is still a favorite for many types of operation.

106 mm. recoiless rifle on an LCM at Son-Ong-Doc, January 1970. The object under canvas behind the breech of the rifle is a minigun in the forward gun tub (photo by author) sthomas2.jpg (62644 bytes)

For the interim heavy SEAL support craft the ubiquitous, reliable LCM-6 was selected for conversion. Extensive is too mild a word to describe the modifications made to suit the two "Mike" boats for their new mission. The engines were heavily muffled, and exhaust gasses piped out below the waterline, while the engine-room was thickly lined with soundproofing material: at low speeds with everything in good condition the boats could not be heard much more than their own length away. The silhouette was reduced by cutting down the duckboarding and removing the characteristic open framework portion of the bow ramp. The electrical system was beefed up to handle a communications installation so complete that the Mikes were frequently designated alternate command posts for the bases from which they operated. A Raytheon Pathfinder radar completed the package, while a small refrigerator and a hot plate provided minimal amenities on transits that could run as long as 20 hours round trip.

60 mm. navy pattern mortar on the LCPL at Sea Float in January 1970. It is capable of indirect fire in the trigger fire and drop fire modes, and of direct fire in the trigger fire mode only. It replaced the hand-held 60 mm. trigger fired trench mortar originally carried. (Photo by author) sthomas3.jpg (59931 bytes)

Armor projection was applied lavishly. The ramp, well-deck, engine-room and conning position were all protected with armor that could stop a .50 cal. armor-piercing round at a range of less than 100 meters, while the engine-room and conning positions were further protected with bar armor and trigger plates to defeat recoilless rifle projectiles and anti-tank rockets. Overhead protection was limited to the conning position and the after two-thirds of the well-deck and consisted of a single layer of splinter-proof plating supported on pipe stanchions.

The armament of these Mikes varied almost from day to day. Since weapons were assigned not to the individual boat but the the detachment operating it, there is no sure way to tell what weapons a particular boat may have mounted for any particular operation. This was particularly true in the early days of their service. The only permanently installed weapons were the 106 mm. recoilless rifle mounted at the forward end of the overhead splinter shield and the Navy pattern 81 mm. mortar mounted in the well-deck just forward of the 106. Initial outfit included four or five .50 cal. machine guns and one or two old .30 cal. machine guns converted to fire the 7.62 mm. NATO standard round. In 1970, towards the end of their lives, the two boats carried the following weapons suits in addition to the big rifle and the mortar:

LCM #1: 
  • 2- .50 cal. MG in a tub between the rifle and the mortar, superfiring over the latter 
  • 6- .50 cal. MG in broadside, 3 on each side behind shields. 
  • 2-M_60 7.62 mm MG at the rear of the conning positions to cover the stern arcs. 
  • 2-40 mm. automatic grenade launchers useable in various positions.
LCM #2: 
  • 1- 7.62 mm Minigun in the tub
  • 4- .50 cal. MG in broadside.
  • 1- .50 cal. MG covering the stern arcs
  • 2- 40 mm. automatic grenade launchers.


Even though LCM #2 carried four fewer weapons in total, she was greatly superior in fighting value, thanks to the minigun, which was to prove its worth on numerous occasions in suppressing hostile fire.

Needless to say, none of these additions and modifications did anything to improve the performance of the basic LCM configuration, modest enough to begin with. On one occasion a 25-mile transit was accomplished in 10 hours, working against a four-to-five-knot current. On occasions the overhead splinter shield was pressed into service as a pick-up point for medical evacuations helicopters, thus proving itself a life-saver in more ways than one.

An LCPL MK IV converted to interim MSSC, photographed by the author at Sea Float in January 1970. This boat has miniguns fore and aft (note ammo boxes), with .50 cal. MG on each beam and a 7.62 mm. MG on the starboard beam. The 60mm. mortar is visible on its pedestal between the minigun turrent and the cabin. sthomas5.jpg (2902 bytes)

Anyone familiar with the workings of the average American sailor mind can imagine for himself some of the nicknames these two boats received on account of the long rifle barrel projecting forward: no less colorful were the epithets derived from a fancied resemblance between the sound of a minigun burst and that of an elephant breaking wind. At is said that no Viet Cong who fired on either of these two Mike boats and survived, was ever stupid enough to try it a second time.

Another view of the HSSC pictured on the title page of this article. sthomas6.jpg (5119 bytes)

The interim medium SEAL support craft was a conversion from the 36-foot, steel-hulled LCPL Mark IV. Four boats were dispatched in-country and won such high reputations for reliability and ability to absorb damage that those detachments equipped with them had to be ordered to give them up after the replacements boats arrived and were in service. The conversion was necessarily less elaborate, owing to the smaller size and single-screw power plant, but within the limitations imposed by size and weight, modifications paralleled those made to the larger LCMs. The engine noise problem was considerably complicated by the presence of two large 'engine access hatches, but a satisfactory solution was found and the smaller boats were even quieter than the LCMs. Quieter, that is, as long as engines, hull and silencing systems were kept in top condition. This was not always possible at some of the advance bases from which these boats operated, and it was often commented that as the noise level rose, so did the weight of armament carried.

Internal armor protection was the same as that in the LCMs, and covered the same areas, but the small size did not permit fitting of the external bar armor and trigger plates. The overhead splinter shield also could be fitted, and several alternative protection expedients resulted in varying degrees of success. Among the less unsuccessful were a sheet of 1/4 inch plywood covered with sandbags, and a tarpaulin pitched like a tent, hove so taut that a grenade striking it would either roll or bounce off into the water.

The smaller size, which limited the passenger and weapons load, naturally meant that in the event of springing an ambush the LCPL was far more vulnerable than the LCM, with far less firepower available to shoot its way out. However, with a far better horsepower-to-weight ratio and a more efficient hull form, the PL could usually (in practice, always) turn downstream and run with the current. Making 15 knots over the ground, the boat could get out of the kill zone' before Charlie had time to develop his full firepower and score a lethal hit.

As Viet Cong forces were reinforced by North Vietnamese regular troops, and their tactics became more sophisticated, and as the boats got older, slower and noisier, the gun packages grew heavier and heavier. The original armament consisted of three .50 cal. MG in broadside and after positions, with two .30 cal. MG converted to 7.62 mm. in a countersunk tub forward. In the cockpit was a sandbox emplacement for a 60 mm. trigger-fired trench mortar. By the time they were withdrawn from service and replaced by the new-construction MSSC, every LCPL carried at least one minigun and a new-pattern 60 mm. direct fire mortar. The last of these LCPLs to withdrawn from service carried two miniguns, the 60 mm. mortar, two .50 cal. MG, one M-60 MG and a 40 mm. automatic grenade launcher. Add to this the personal weapons of the embarked SEALs firing over the bulwarks where the cabin overhead was removed and you have one of the most powerful concentrations of firepower ever put into a small boat.

A number of other weapons were tested on the LCPLs, including the 75 mm. and 57 mm. recoilless rifles, and various combinations of aircraft rocket pods. Proving more dangerous to the boat than to the enemy, they were quietly forgotten.

The PLs were lucky: there is no question about that. One, caught in an ambush en-route to the objective area with SEALs still embarked, took more than 200 holes in the hull. Of the 13 men aboard, 12 were wounded, none seriously. One hit, from a 57 mm. recoilless rifle, passed completely through the hull, ripping open a fuel tank, before exploding on the far bank. Despite their damage and casualties, the SEAL and MST personnel turned around and fought their way clear, killing or wounding more than twice their own number out of a hostile force estimated at company strength, and at ranges of 25 meters and less.

The personnel of Mobile Support Team TWO who manned these six boats and their replacements, were members of Boat Support Unit ONE, from Naval Amphibious Base, Coronado, California. They were assigned to duty in Vietnam on a 180 day temporary duty basis. MST and SEAL personnel returned to Vietnam so frequently that most of them spent more total time there than 95% of the forces assigned on a permanent duty basis.

The full story of SEAL and Mobile Support Team operations cannot yet be told. The tactics and techniques are still too potentially useful to risk disclosing them to unfriendly powers. There is also the need to protect our friends; many operations were made possible only by the voluntary co-operation of Vietnamese civilians, peasant farmers and fisherman, whose lives would be forfeit if their actions were to become known to the VC or the NVA.

Of the six boats described above, none still exists. LCM #1 sank when heavy seas pounded her against the tender to which she had been assigned for overhaul. LCM #2 was found to be so thoroughly worn out that repairs would have come to more than the cost of replacement. Three of the LCPLs were in a similar state, and wound up as anonymous pieces of scrap on some Vietnamese junk heap. 

The fourth, in substantially better condition, had been stripped and was lying alongside a pier, awaiting transfer to the Vietnamese Navy, when a carelessly-operated tug tore her loose from her moorings. The empty, powerless hull was seen to capsize just before drifting out of sight around a bend, nevermore to be seen. There are those of us, though, who look forward to hearing any day now of a 'Flying Hoa-Ky' (American), running the rivers of South Vietnam, raising hell and the dead with its unmistakable stench of a diesel engine long past due for overhaul.

A minigun installation as found on the LCPL based at Rach Soi in January 1970. In this boat the minigun ammo box is located under the forecastle deck, rather than above and behind the turret. The pedestal and recoil cylinder of the mortar are visible behind the gunner's head. (Author's photo) sthomas4.jpg (48838 bytes)

It will never redound to the U.S. Navy's credit that the (then) most powerful navy in the world had to resort to such makeshifts to carry out a mission , but it will always be a source of pride that sailors did so much with such jury-rigged tools. Until now these first six SEAL support craft have been almost completely unknown outside the special warfare community, and even there they are slowly being forgotten--the Mobile Support Team has been disbanded, its personnel scattered and for the most part discharged, and the SEALs are busy training for other missions they hope will never have to be carried out. Still, the six old warriors were the first in a new family of specialized riverine and estuarine warfare craft, and they deserve to be remembered, if for no other reason than that.



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