© 2004 Robert H. Stoner - used by permission
Special Warfare: Small Combatant Craft Development – World War 2 through
GMCM (SW) Robert H. Stoner (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 late 1963. 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
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. The IBS was employed for short-range operations.
Originally called the Landing Craft Rubber (Large), this inflatable rubber boat became known by the more common term – IBS for Inflatable Boat, Small. 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.
The next step up was the landing craft personnel (LCP),
landing craft personnel, ramped [LCP(R)], or Landing Craft Personnel, Large
(LCPL). Higgins in
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.
The LCP(R) 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.
A World War 2 photo of the LCP(R) with a full troop load. (Photo: US Navy)
Both LCP and LCP(R) were used to drop off and pickup swimmers. To do this, the LCP or LCP(R) [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.
This means of extraction was used from the end of World
War 2 through the Korean War and into the 1960s. However, the method exposed the boat, crew,
and swimmers to hostile fire (the pickup boat was limited to 12 knots) and
swimmers readily sustained injuries while being brought aboard. In the early 1960’s the Navy fielded two gas
turbine-driven boats that employed the
Above. A portside shot of a 52-foot LCSR. Seven LCSR and two LCSR(L) boats were built. Uniflite of Bellingham, WA built the fiberglass LCSR. The LCSR and LCSR(L) were the Navy’s first attempt to put gas turbines in small craft. The effort was not entirely successful. The LCSR turbine exhaust had a nasty habit of setting fire to wooden piers or small boats that came alongside. The clutch mechanism for connecting the output of the turbines to the shafts was temperamental. Props had a nasty problem of throwing blades – into the lazerette where the steering gear was located. Low battery output caused hot starts on the turbines that lead to shortened engine life. (Photo: US Navy)
One of the two 36-foot
LCSR(L) craft showing the exhaust stacks for the gas turbine engines. One boat was fiberglass and the other was
aluminum. LCSR(L)-1 was built by Harbor Boat Co. (Harco) of
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 LCP(R) boats were phased-out in the late 1950’s, the LCPL became the workboat for UDT units. When attached to ships, the LCP, LCP(R), and LCPL were usually employed on converted World War 2 destroyer escorts called APD’s (high-speed destroyer transports). 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.
A late 1966 photo shows a
nest of Mk IV LCPLs is tied up along side the USS BELLE GROVE (LSD-2). These steel hulled 36-foot boats are stock except
for the mounted machine guns. The first
SEAL units in
A 1967 shot of the
High-Speed Destroyer Transport USS DIACHENKO (APD-123). Converted from World War 2 destroyer escorts,
the APD carried four 36-landing craft and were very useful for supporting UDT
operations with their 5-inch and 40mm guns.
However as SEAL operations moved ashore and onto the rivers and canals
Late 1966 and early 1967 saw the first deployment of UDT
and SEAL teams to the
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 40mm grenade launcher.
Below. A rare 1967 shot of the LCPL Mk IV used by
SEAL Team ONE in
Above. Another rare 1967 shot of the LCM-6 modified by SEAL Team ONE. 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 M3 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: Chuck LeMoyne)
Above. A later 1967 portside shot of the LCM-6
modified by SEAL Team ONE known as the “
The standard 56-foot LCM Mk 6 as it was before SEAL Team ONE modified it. (Drawing: US Navy)
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 two 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 Can Tho and later 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.
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.
The STAB used by SEAL Team TWO in 1967. (Photo: US Navy)
A bow-on shot of a well-used STAB. (Photo: Fred Schuler)
SEAL Team TWO and MST brought three STAB (SEAL Team
Assault Boats) to
The old and the new -- a
MST-modified LCPL and a new LSSC are tied up to a barge in the
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 M60 machine guns, several single M60 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).
A bow-on shot of Detachment ECHO’s LCPL. Note the cargo net tied on the bow to assist the SEALs when reboarding the craft. This boat has an interesting in-country modification (and the only one of the four LCPL’s to receive it): the 7.62mm Mini-gun. To its rear is the Mk 4 Mod 0 60mm Naval mortar. To the left of the crewman are an Mk 20 Mod 0 40mm automatic grenade launcher and a Browning .50 AN/M2HB machine gun (one of two). ECHO’s LSSC is just visible in the left foreground. (Photo: John Engstrom)
A shot of LTjg
Engstrom’s LCPL extracting from a beach on the Song Cau Lon near
Detachment ECHO’s LCPL
with its bow on the beach and its SEALs ashore.
The dense jungle is one reason why the Commander Naval Forces
A close-up view of the Mini-gun and gunner on Detachment ECHO’s LCPL. The Mk 4 Mod 0 60mm mortar is in the foreground. (Photo: John Engstrom)
The Detachment ECHOL LCPL
underway with the SEALs aboard. The
location is unknown but the buildings suggest along the
The Detachment ECHO LCPL
shows its battle damage after a dust-up with the local VC/NVA forces. Just to the left, middle of picture, above
the waterline is the hole from a B-40 rocket.
Also visible are numerous bullet impacts on the hull. This boat reflects the upgrades in armament
SEA FLOAT in late 1969 or
early 1970. The barges were oriented
East to West in the
The extent of defoliation along the river at SEA FLOAT to prevent the VC/NVA from ambushing friendly forces is very apparent in this photo. This did not prevent the bad guys from shooting at us on the river – it merely made it harder for them to hide and get away with it. (Photo: Bob Stoner)
The next series of photos show the result of PROJECT ZULU: the Heavy Seal Support Craft or HSSC. (The HSSC evolved as experience was gained in fighting the enemy along the river. Compare this boat with the Nha Be LCM-6 of SEAL Team ONE.
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 supplemented 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)
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)
Another shot of the HSSC 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)
A good side view of the HSSC in early 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. It has yet to receive its 106mm recoilless rifle and Mini-gun. (Photo: US Navy)
The HSSC in mid-1969,
before the bar armor modifications. Bar
armor was standard on the HSSC assigned to SEA FLOAT. In this shot, the solid helo pad has been
added over the well deck. A M40A1 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. By the time
the HSSC got to
The other (second) HSSC was similar in appearance except that it had twin .50 M2HB machineguns in place of the Mini-gun. Ordnance carried by this HSSC was the was the 81mm/.50 forward, twin .50 BMG in a gun tub behind it, two pairs of .50 and two pairs of M60 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. This HSSC was later turned over to the Vietnamese Navy. (Photo: Vietnamese Navy)
“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 M72 rocket launcher (or LAW – light anti-tank weapon) being fired. The M40A1 106mm recoilless rifle is swung to starboard in preparation for firing. This beast was MUCH louder than the M72! (Photo: Steve Elson)
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 17-foot Boston Whaler was unsuitable, as was the longer STAB trimaran. The LCPLs and HSSCs 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 (MSSC). Grafton Boatworks built 16 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.
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. These two STAB’s are alongside the
USS BENEWAH (APB-35) on the upper
A slightly damaged photo of a STAB beached. The area is apparently secure since the guns are still covered. (Photo: Don Basillion)
Morning on the
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: Gary Hunt)
Low tide at
BM3 Dan Savage of Detachment GOLF (September 1970 to March 1971) shows off the battle damage to his LSSC: 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)
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)
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)
A classic SEAL insertion
from the LSSC. The lead SEAL carries the
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
Detachment ECHO’s LSSC at
A January 1971 photo of
Detachment CHARLIE’s LSSC at SOLID ANCHOR after an ambush. The SEAL advisor LT Jim
A good interior shot of the MST-2 Detachment at Nha Be in 1969. (Photo: Terry Knott)
Two of the Nha Be LSSC’s nested along the river. Note the mixed armament carried; both M60 and M60D 7.62mm machine guns, an M2HB Browning .50 machine gun (right); and a Mk 20 automatic 40mm grenade launcher (left foreground). (Photo: Terry Knott)
Interior shot of the two
nested Nha Be LSSC’s. The throttles are
just below the radome. Note the C-ration
cans clipped to the sides of the M60D machine guns to help the belted
ammunition feed to the gun. This was a
frequent field expedient in
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)
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)
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 cubic 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.
Stateside shots: The MSSC at the Boat Support Unit ONE pier in
A public relations shot of the MSSC dropping off SEALs on Silver Strand Beach near the Amphibious Base at Coronado, CA. (Photo: US Navy)
Detachment ALPHA’s MSSC getting ready to move out on a daylight operation from Ben Tre (during October 1970 to March 1971). (Photo: Gary Hunt)
Stern shot of Detachment ALPHA’s MSSC heading out on the same daylight operation from Ben Tre. (Photo: Gary Hunt)
Detachment ALPHA’s MSSC at top speed on the river near Ben Tre. Note the cargo net draped over the bow to assist SEALs in getting aboard the boat on extraction. (Photo: Gary Hunt)
CWO Shepherd of Detachment ALPHA and the crew of their MSSC at Rach Soi. Note the Naval Mk 4 Mod 0 60mm mortar on the starboard weapons mount. This installation was not common. (Photo: Gary Stubblefield)
Detachment ALPHA’s MSSC at the Rach Soi docks. Other river craft in the photo are a
Interior of Detachment
ALPHA’s MSSC looking aft shows off the amidships .50 BMG’s and the aft 7.62mm
Mini-gun. Note the M79 grenade launcher
behind the bungee cord across the Mini-gun’s ammo container. The 40mm grenades are in the bandoliers just
to the left of loop in the Mini-gun’s feed chute. The box [left foreground] with the large “C” is
for C-rations, while an insulated cooler is directly in back of it. The flak curtains on either side of the well
deck are clearly shown in this photo.
(Photo: Gary Hunt)
A recycled .50 machine gun. This gun was captured from the VC and put back to work against them. The hybrid AN/M2-M3 (Aircraft) Browning machine gun is on Detachment CHARLIE’s MSSC. (Photo: Bob Stoner)
The MSSC’s of Detachments
CHARLIE and BRAVO nested on the beach at SOLID ANCHOR in October of 1970. In the Spring of that year, Detachment
CHARLIE’s MSSC (foreground) took a hit with a B-40 rocket just above the water
line and behind the white fender that
severed the steering cables (narrowly missing the fuel cell), punched through
the interior armor and flak blanket, and wounded one of the SEALs. The emergency tiller was quickly attached and
the boat was maneuvered out of the ambush.
One of CHARLIE’s two LSSC’s is just behind the folded down windshield. The remains of the old SEA FLOAT barge
complex can be seen to the right, still anchored fast in the
Below. Detachment CHARLIE’s MSSC hull showing the B-40 hit. (Photo: Fred Schuler)
Interior shot of the MSSC showing damage to the ceramic armor ties and flak blanket. (Photo: Fred Schuler).