Naval Special Warfare:
Small Combatant
Craft Development History
By
Robert H. Stoner, GMCM (SW) (Ret)
In order to understand how the UDT/SEAL/MST units evolved during the Vietnam War, we have to understand how things were done in the beginning.
Boat Support Unit ONE got into the Naval Special Warfare role through its operation of fast patrol boats (PTF) beginning in early 1964. As the small craft types multiplied for the prosecution of the war, BSU-1 became heavily involved in the training of crews to man the boats. Meanwhile, across the road separating the Coronado, CA Amphibious Base and the UDT/SEAL compound other things were happening.
Underwater Demolition Teams had evolved from the Navy Combat Demolition Units of World War 2. As constituted, the UDT had small boats for accomplishing their mission. The smallest of these was the IBS (or small inflatable boat). The IBS was an 8 to 10-man raft that could be fitted with a small outboard engine.
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Originally called the Landing Craft Rubber (Large), this inflatable rubber boat became known by the more common term – IBS. As shown, the IBS had a pointed bow that, over time, became more blunt. Over the decades the IBS was in use, its overall length of 16 feet, 8-foot beam, nil draft, and 396 pound weight (or 474 pounds with a 9-1/2 HP outboard) remained fairly constant. Speed was roughly 4.5 knots with the outboard and 55 yards per minute with eight experienced men paddling. The IBS was the workhorse of NCDU/UDT/SEAL units until it was replaced by the Zodiac series of inflatable boats.
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The next step up was the landing craft personnel (LCP), landing craft personnel, ramped (LCPR), or Landing Craft Personnel, Large (LCPL). Higgins in New Orleans, LA, had designed the original boats during World War 2 for amphibious use. All the boats were 36 feet long, wood or steel construction, and powered by 6-cylinder diesel engines. The LCP had a blunt, tapered bow for running up on beaches. The single propeller and rudder were protected by a skeg attached to the keel. Immediately in back of the bow were two, three-foot diameter holes in the deck that mounted .30 machineguns. In back of the gun positions was a conning station (left hand front corner of the well deck that carried the troops. The engine was located under a cover in the center of the well deck and the fuel tanks were located aft. Troops exiting the LCP had to jump over the side and wade to the beach. The boat was made primarily of wood with a Ľ-inch thick “armor” plate attached to the sides of the craft.
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Drawing of the LCP (aka “Higgins” boat) as used at the start of World War 2. Lack of a bow ramp meant troops had to exit by jumping over the side. The boat was soon replaced by the LCP(R) and these boats were used by the first NCDU/UDT units.
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The LCPR was a modified version of the LCP. The bow got blunter and became a ramp. There was a connecting passage between the well deck compartment and the ramp that allowed troops to exit from the bow of the boat. The twin machine gun positions were located similarly to those on the LCP. There was an inner safety door that separated the bow ramp from the interior well deck to prevent unintended flooding of the boat. The boat was also made of wood with a Ľ-inch thick “armor” plate attached to the sides of the craft.
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A World War 2 photo of the LCP(R) with a full
troop load. (Photo: US Navy) Both LCP and LCPR were used to drop off and pickup
swimmers.
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To do this, the LCP or LCPR [and later LCPL] moved parallel to the beach with and IBS lashed along side. Swimmers would go over the side of the LCP or LCPR, into the raft, and would roll-off into the water for insertions. For extractions, a husky UDT man would man the raft holding what looked like an oversized tennis racket without strings. The Swimmers would line-up at a given interval, one behind the other, and hold up their arms. As the pick-up boat moved down the line the swimmers stuck their arms into the “tennis racket” and were hauled onto the IBS lashed to the side of the moving boat. The swimmer would exit the raft for the pick-up boat to allow another swimmer to be recovered.
The LCPL was a general-purpose craft. It was used as a picket boat to help guide other landing craft during amphibious operations, it was used as a captain’s gig on ships, or when really spiffed-up as an admiral’s barge. The LCPL Mk IV was a conventional steel hulled boat with a cabin mid-ships. The cabin was used as a conning station and as a weather cover for the transportation of personnel. As the wartime LCP and LCPR boats were phased-out in the late 1950’s, the LCPL became the swimmer recovery boat for UDT units. When attached to ships, the LCP, LCPR, and LCPL were usually employed on converted World War 2 destroyer escorts called APD’s (auxiliary personnel, destroyer). It was usual that the UDT detachments provided their own boat crews for operations or acted to train ship’s company boat crews from the APD’s for their particular kinds of operations.
Late 1966 and early 1967 saw the first deployment of UDT and SEAL teams to the Viet Nam war zone. At first, the UDT/SEAL operators made do with a scrounged collection of small boats:
There was the ubiquitous IBS and its parent, the LCPL. UDT/SEAL operators modified the LCPL Mk IV to carry two .30 and two .50 machine guns, and one Mk 18 crank-operated 40mm grenade launcher (on the boat’s centerline, between the two .30 machine guns). The boat was pretty much stock and there was none of the specialized armor or armament that characterized other such boats later in the war.
Similarly, they acquired a mechanized landing craft (LCM-6) and modified it to carry three .30 and four .50 machine guns, a 57mm recoilless rifle, a 60mm mortar, and an Mk 18 crank-operated grenade launcher.
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The standard 56-foot LCM Mk 6 as it was before ST-1 modified it. (Drawing US Navy)
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A rare 1967 shot of the LCPL Mk IV used by SEAL Team ONE in Viet Nam. The boat is pretty much stock with .50 BMGs fore and aft with .30 BMGs mid-ships and the Mk 18 on the centerline, between the two .30
BMGs. (Photo by LeMoyne).
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Another rare 1967 shot of the LCM-6 modified by ST-1. Looking aft from the bow, the Mk 4 Mod 0 60mm mortar is covered by a flak jacket and canvas cover, while the Mk 18 Mod 0 40mm (Honeywell) grenade launcher is just in back of the flak jacket. The mid-ships .50 BMGs are shown; one just behind the Mk 18 and the other under a camouflage cover. Both these guns were mounted on the ground M-3 mounts. The M18A1 57mm recoilless rifle is mounted just above the rear canopy. Mounts and shields for two of the three aft .30 BMGs are clearly seen; the left gun is at full depression while the barrel of the right gun is slightly elevated with a cloth covering the receiver (just above and behind the camo cover for the .50 BMG. Not shown are the two .50 BMGs on either side of the bow ramp or the .30 BMG that fired directly aft. (Photo by
LeMoyne)
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Two things were apparent from the first: (1) the UDT/SEAL operators needed better, purpose-built craft with more firepower and armor, and (2) the boats needed to be driven by sailors – other than UDT/SEAL operators – who were familiar with the kind of tactics that were being developed. This need developed into what was called PROJECT ZULU.
Volunteers from BSU-1 deployed to Viet Nam to experiment with the support of UDT/SEAL operators under wartime conditions. They began with one LCM-6, two Mk IV LCPL’s and four Boston Whalers (with silenced outboards). The Whalers were fitted with a pedestal mount that could take either a .30 or 7.62mm machine gun. The LCPL’s and LCM-6 (now christened the Heavy SEAL Support Craft) were modified to accommodate numerous gun positions and had armor added to protect vulnerable spaces. The heavily modified LCPL’s and HSSC were based at CanTho and My Tho. Their operational area was a swamp, much like the Florida Everglades, that was infested with Viet Cong guerilla units. This was the RSSZ [Rung Sat Special Zone]. It was here that the early SEALs and BSU-1 (now called Mobile Support Teams – MST) sailors learned the trade of war.
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A Boston Whaler with an all-Vietnamese crew on patrol. (Photo Vietnamese Navy)
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With the exception of the Boston Whalers, the LCPL and HSSC were very slow. The problem with the Whalers was their total lack of armor and firepower for SEAL operations. Something better was needed.
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The STAB used by SEAL Team TWO in 1967. (Photo US Navy)
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SEAL Team TWO brought several STAB (SEAL Team Assault Boats) to Viet Nam in 1967 for evaluation. The STAB was a modified commercial design. It had twin outboards, some armor, and more mounts for M-60 machine guns. It was not entirely successful and was an interim design at best.
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The old and the new -- a MST-modified LCPL and a new LSSC are tied up to a barge in the Bassac River at Nha Be or My Tho in late 1968 or early 1969. This LCPL has a single .50 BMG forward with a pair of .50s mid-ships. Viet
Nam was always hot with humidity that seemed to take your breath away along its rivers and canals. The only exception was during the Monsoon season, when temperatures could drop twenty degrees or more to the point you were cold, you shivered, and your teeth chattered. From looks of the boat crews, this is not the Monsoon season. (Photo: Rick Erwin)
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Meanwhile, modifications were being done to the LCPL’s in-country (now four) and the HSSC as the result of combat lessons learned.
The LCPL was the workhorse of the MST units during late 1967 through 1969. Modifications included cutting a hole in the foredeck for single or twin .50 machine guns or a 7.62mm Mini-gun. The deckhouse was cut down to reduce its visibility. A canopy was erected over the interior to shield the occupants from the tropical sun. A Raytheon 1900 search radar was fitted to help identify small craft and assist navigation. A 60mm Naval mortar, three more .50s or two .50s and twin M-60 machine guns, several single M-60 machine guns, a Mk 20 automatic 40mm grenade launcher, and AN/TVS-2 night vision gear. The next series of photos are show details of the LCPL belonging to LTjg John Engstrom’s Detachment ECHO in operations at Nam Can before the building of SEA FLOAT (December 1968 to June 1969).
The next series of photos show the result of PROJECT ZULU: the Heavy Seal Support Craft or HSSC (also known as “Mighty Mo”). The HSSC evolved as experience was gained in fighting the enemy along the river.
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The HSSC as she looked at the time of PROJECT ZULU. She does not yet have the later in-country modifications such as bar armor. Note the standoff-plates around the conning station of the boat (beneath the radar dome). The solid plates would eventually be replaced by bar armor that was lighter and more effective. Likewise, the canvas covering over the well deck would give way to a steel helicopter pad and a canopy would soon be erected over the conning station to protect the crew from the Vietnamese sun. The armored bulge around the engine spaces is also absent in this picture. Note the two LCPL’s of PROJECT ZULU nested outboard of the HSSC. (Photo: US Navy) |
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A close-up of the HSSC’s conning station. Note the armored cupola with vision slits and the improvised canopy to protect the crew from the sun. The radar dome appears to have been relocated in this photo. Two members are “catching some rays” on this river transit. (Photo: US Navy) |
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Another shot of the Nha Be HSSC “Mighty Mo” seen from the bow ramp. Note the inner blast doors to protect the well deck when the ramp goes down. There are two 7.62mm Mk 21 Mod 0 Browning machine guns directly to the rear of the Mk 2 Mod 0 81mm mortar (the basket-enclosed breech end is just to the left of the sailor wearing the helmet and flak jacket). Behind the Mk 21’s are the four .50 machine guns (two per side) and there was a single .50 firing out the rear of the conning station. The well deck does not yet have its canvas cover replaced by the helicopter pad in this 1968 shot. (Photo: US Navy) |
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A good side view of the HSSC in late 1968 shows protection upgrades around the engine compartment to defeat rockets and recoilless rifle rounds. No bar armor is fitted at this time and the cloth cover over the well deck has yet to be replaced. (Photo: US Navy) |
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The Nha Be HSSC in 1969, before the bar armor modifications that became standard on the other HSSC assigned to SEA FLOAT. In this shot, the solid helo pad has been added over the well deck. A M-40A1 106mm recoilless rifle is mounted on the pad and a 7.62mm Mini-gun has been added in a tub at the front of the pad to give the HSSC more frontal firepower.
The Mk 2 Mod 0 is in front, barrel pointing down to drain any rainwater. The
HSSC used at Nam Can [SEA FLOAT/SOLID ANCHOR] was similar to the Nha Be HSSC
except that ours had bar armor all around the hull and around the conning
station. Also, our bow ramp was cut lower than that of the Nha Be boat and we
used the Mk 2 Mod 1 mortar with a piggyback-mounted .50 BMG. Ordnance carried by
Nam Can’s HSSC was the was the 81mm/.50 forward, the Mini-gun in a gun tub
behind it, two pairs of .50 and two pairs of M-60 machine guns on either side of
the well deck, a 106mm recoilless rifle on top of the helo pad, and a .50 “stinger”
machine gun at the rear of the conning station. (Photo: US Navy) |
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“Fire in the hole!” Steve Elson, a Nha Be SEAL took this photo of target
practice from the helo pad of the HSSC. Note that
everyone with experience is protecting his ears from the
back blast of the M-72 rocket launcher (or LAW – light
anti-tank weapon) being fired. The 106mm recoilless
rifle is swung to starboard in preparation for firing.
This beast was MUCH louder than the M-72! (Photo: Steve
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The MST sailors and SEALs learned that the B-40 rocket and 57mm or 75mm recoilless rifles were some of their worst enemies. By late 1969 the HSSC had benefited from the anti-rocket protection afforded to the craft of the Mobile Riverine Force. Bar armor made from concrete reinforcing rods was placed on hangers a foot away from the hull and pilothouse of the boat. The bar armor would detonate the warhead of the rocket or recoilless round to prevent its penetrating into the interior.
By late 1967 it was obvious that the Boston Whaler was unsuitable, as was SEAL Team TWO’s STAB. The LCPL and HSSC certainly had firepower, but they were very slow. Additionally, their size and draft prevented them from going into the smaller canals. And so it was back to the drawing board. What came forth were the two boats that became the workhorses of the MST/SEAL units for the remainder of the war in Viet Nam. These boats were the Light SEAL Support Craft (LSSC) and Medium SEAL Support Craft. Grafton Boatworks built sixteen LSSC’s and Atlantic Research built Ten MSSC’s.
Grafton also built 22 of a slightly larger, improved [aka Mk II] version of the LSSC called the Strike Assault Boat or STAB. [Note: there are two STAB boats of different designs used by different operators. This has confused many people and authors over the years.] These STAB’s were assigned to STAB Squadron [StabRon] 20 that operated around the “Parrot’s Beak near the Cambodian Border in 1970 and not to MST.
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The second STAB (aka Mk II LSSC), like the original LSSC, was also built by Grafton Boatworks. It was two feet longer and used MerCruiser outdrives (props) instead of Jacuzzi pump jets. These STAB’s were used exclusively by StabRon 20 and were not used by MST. (Photo: Tom Lefavour) |
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The LSSC of MST Detachment ALPHA comes back in from an operation with SEALs of X-Ray platoon aboard. It appears that the radio operator standing on the bow may have a problem judging from his expression and posture. Note the diverse “uniforms” worn by the SEAL and MST operators. The general rule was that if it worked you used it; if not, you didn’t or found something better. Hence, SEALs wearing Levi’s instead of camouflage trousers. (Photo: Gerry Hunt) |
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Low tide at Nam Can. The LSSC of Detachment ECHO has its underwater vitals exposed for maintenance. Even routine tasks could be difficult due to the lack of support equipment. Note the Jacuzzi pump jets and the step that are different from the later STAB. (Photo: John Engstrom) |
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The Long Phu Detachment GOLF (April to September 1970) LSSC shows off its battle damage: a B-40 rocket hit just below the pad eye. The pad eye deflected the blast away from the crew and no casualties occurred. (Photo: US Navy) |
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Close-up of the B-40 hit on the Detachment GOLF LSSC. The rubber railing that ran along the edge of the deck on the LSSC is clearly shown in this picture. (Photo: US Navy) |
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An LSSC and LCPL underway for a SEAL operation. A Vietnamese LDNN (SEAL) is on the bow. The SEAL facing the camera clearly shows his subdued UDT life jacket. In this 1968 photo, the radar has yet to be removed from the LSSC. (Photo: US Navy) |
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A classic SEAL insertion from the LSSC. The lead SEAL carries the Ithaca M37 12 gauge shotgun. The second SEAL is barefoot to confuse VC/NVA trackers. (Photo: US Navy) |
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Not all SEAL extractions were easy; sometimes you had to push the boat [here an LSSC] off the beach when the tide started to drop. The mangrove swamp is typical of the Mekong River Delta and the canals of the Ca Mau Peninsula. (Photo: US Navy) |
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Detachment ECHO’s LSSC at Nam Can. Note that it still has its radome in this early 1969 shot. Here, an improvised twin M-60 mounting has replaced the single rear .50 BMG set-up. (Photo: John Engstrom) |
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A flying LSSC? Certainly! In this photo, an LSSC is about to be airlifted by an Army CH-47 “Chinook” helicopter. The idea was to insert and extract the LSSC into areas that the VC/NVA considered secure from enemy forces. The idea was tested three times; the first two flights were successful and the third resulted in the jettison of the LSSC when it began an uncontrolled oscillation beneath the helicopter. A fourth flight was not attempted. None of the attempts involved combat operations. (Photo: US Navy) |
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The LSSC in flight beneath a CH-47 helicopter. This unique view of the LSSC shows why it was able to go into very shallow water – there was nothing projecting below the bottom of the hull due to its water-jet propulsion system. The inlet for the portside pump is seen near the end of the hull. (Photo: US Navy) |
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The supplement and then replacement for the venerable LCPL was the Medium SEAL Support Craft (MSSC). Ten were built by Atlantic Research for the Navy under a 1968 contract and came into use by MST in late 1969. The MSSC could carry a whole SEAL platoon plus its MST crew at speeds over 30 knots. The MSSC was built of aluminum like its LSSC stable mate, but instead of the two 427 cu. Inch Ford engines and Jacuzzi pump jets, the MSSC used 427 cu. inch Chevrolet engines with MerCruiser stern drives (outdrives). The MSSC could not go into the shallow waters the LSSC could, but the thrust of its propellers was more than that of the Jacuzzi pumps in the LSSC.
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