The Large Slow Target

Amphibious warfare has long been considered one of the forms of warfare most inviting of disaster to the attacker. History has plenty of examples of failed assaults on foreign shores. The preeminent modern example is Gallipoli during the First World War.  After that failed campaign, many military minds declared amphibious warfare dead and buried. But as Germany overran all of Europe in 1940, planners and strategists in England and American figured they’d better dig up its corpse and find a way to revive it, or the war was effectively over.

The problem of getting assault infantry ashore was fairly simple. Boats had been used for that purpose for a long, long time. The real challenge was getting enough follow-on forces ashore to defeat a counterattack, and to establish sufficient logistics pipelines to keep those forces supplied with food, fuel and ammunition. The practice had been through the years to land near a port, envelop that place, and unload follow-on waves in a conventional manner. But the vast increase in firepower of modern armies in the 20th century, coupled with their much greater mobility thanks to motorization, meant that conventional forces would be unable to move swiftly enough to capture a port before they were destroyed by counterattacking German forces. Further, as planners in England looked at the maps, the poor quality of most French ports was quite dismaying. Only a handful of ports had any real capacity at all. That meant the German armies could be concentrated on defending those points. A landing anywhere else would be pointless, and go nowhere, stagnating on a beachhead, and inviting counterattack and destruction at the German’s leisure.  And trying to seize a defended port was prohibitively costly, as the raid on Dieppe would prove in 1942.

Clearly, any amphibious assault would have to bring with it similar firepower and mobility as the defender almost from the very first instant. But getting tanks, artillery, and trucks ashore across an unimproved landing beach is a far more difficult proposition than putting ashore infantrymen.  Early on, the approach was to simply use slightly larger landing craft to carry ashore a tank. The problem was getting the tank from the ocean-going vessel into the landing craft. Boom capacity on most ships was insufficient to safely lift even early tanks, and as the war progressed, tanks kept getting heavier and heavier. And even when the booms had capacity, it was slow. Worst, safely lowering a tank from a ship into the tiny well of a landing craft was almost impossible except under conditions of dead calm. For that matter, storing tanks in the cargo holds of most ships wasn’t particularly efficient.

British planners especially, but American ones as well, put a great deal of effort into solving these problems. One approach was to use sea-trains. Basically a sea-train was a giant ferry onto which the rolling stock of a railroad was simply rolled aboard onto rails much like a marshaling yard built onto the main deck of an oceangoing ship. If you could roll boxcars onto one, it seemed reasonable that you could roll tanks onto one as well. Similarly, large ferryboats were considered. This solved the problem of transporting tanks most of the way. The trouble was unloading them. If a port or wharf could be seized, unloading was possible. But the whole point was, ports or wharfs were not available.

The ever innovative British began to grasp a solution to the problem. If a ship could be brought close enough to shore, a ramp or causeway might be laid over the bows and tanks allowed to simply drive ashore. But the hulls of most oceangoing ships were had far too much draught to allow them to close up to beaches suitable to assault. Most beaches suitable beaches had very shallow gradients, and would require causeways far longer than the ships themselves. The need for a very shallow draft ship became clear. Looking through Lloyd’s registry, they grasped upon a small series of shallow-hulled tankers built to cross the sandbars at the mouth of the Orinoco River to service Venezuela’s oil industry. These small, flat bottom tankers could be adapted both to carry tanks on their decks, and come sufficiently close to shore that a workable ramp became feasible.  But the fleet of these specialized tankers was far too small to suffice. Britain’s shipbuilding capacity was already overwhelmed trying to build conventional merchantmen and escorts for the North Atlantic. So they turned to the US Navy for help.

The US Navy, since it would have to build new ships from scratch anyway, decided that while the British were on the right path, more could be achieved. Working hand in glove with British naval architects, a series of designs were drawn up, discussed, critiqued, improved, tweaked, and refined. As the ships would come to be used by both countries, the needs of both nations were carefully considered when settling on design elements. Eventually, they would fix the design of what would come to be known as the Landing Ship, Tank, or LST.  Rather than storing tanks on the top deck, instead, they would be stored on the bottom deck, well inside the hull. And rather than disgorging them from a ramp over the bows, the bow itself would have doors that opened, and a small ramp would allow the tanks (and trucks or whatnot) to drive ashore. And with the top deck no longer storing tanks, it could be used to store trucks or cargo. An elevator (later a ramp) would allow trucks to be lowered to the tank deck, and then driven ashore.


LST discharging cargo over the beach

Any ship design is a series of compromises. The LST had to be capable of safely crossing entire oceans while fully loaded. This calls for a deep draft. But the LST  had to be of very shallow draft, especially forward, to allow it to beach along shallow shores.  The solution to this contradiction was two-fold and simple. While the LST was intended to deliver about 500 tons of cargo ashore, when sent upon the great oceans, it was usually travelling from the US to a staging area such as England or North Africa. Accordingly, they were loaded with up to 2500 tons of cargo. This saved shipping space on merchant shipping. It also gave the LSTs greater draft during the crossings. They would be unloaded, reloaded with an assault element, and the rest could come in follow up waves. The other part of the solution harks back to the LSTs roots as a tanker. Large numbers of ballast tanks were installed, and could be quickly either filled or emptied of seawater, allowing the LST to adjust its draft to suit its environment. Indeed, often the bow of an LST would be very lightly trimmed, with the stern fairly heavily trimmed, with that “nose up” attitude allowing it to get even closer to shore before running fully aground.

Two other major compromises in the design bear discussion. The first of these is horsepower. The single most critical bottleneck in shipbuilding wasn’t steel (though it was a major task allocating steel between competing needs) but horsepower. There were several different power plants that might have been used to power the LST. The traditional power plant of the Navy, steam, was considered. Steam power plants are compact and for a given weight, generate excellent horsepower. But the bottleneck there is that turbine powered steam plants require turbines and reduction gears. Turbines were hard enough to make. But reduction gears, to transfer the power of low torque, rapidly spinning turbines to high torque, slowly spinning ships propellers, took time to build. And there was
a very finite limit on the numbers of reduction gears that could be cut. Triple expansion steam engines might have worked. These look a lot like a giant piston engine in your car, but rather than gas and air moving the pistons, steam is injected into them to provide motive power. But TES engines were difficult to maintain, and far less efficient than steam engines. Further, the majority of TES engines were already allocated to the massive Liberty ship program. That left diesel engines. Large diesel engines were only just beginning to become reliable enough to enter widespread service. Previously, they had primarily been used only for submarines. They did have certain advantages. They were incredibly fuel efficient (compared to steam). They also required a good deal less maintenance and manpower to operate. Their simplicity of use would be important given that most of the men who would operate LSTs had never even seen the ocean, and would have a very brief period of training. Most importantly, they were available.

But there was a serious drawback to diesel power as well. Diesel power plants weren’t very… powerful.  The engine eventually chosen to power LSTs, the GM EMD 12-567 only produced about 2000 horsepower. Twin engines gave the LST a top speed of about 12 knots. Now, understand, increasing horsepower wouldn’t have increased the ship speed all that much. The basic hull design of any ship imposes a practical top speed. Beyond a certain point, increases in horsepower yield diminishing returns. Doubling the LST horsepower might have only yielded another knot or so of top speed. But the requirement that the LST be able to beach on shallow shores set the hull shape, and imposed that practical upper limit on speed.*

That hull shape leads us to the second great compromise, the hull shape. The single largest consideration in choosing the lines of the hull was the needed ability to beach the ship. That called for a flat bottom with a relatively bluff front.  Aside from limiting the ships speed, it also guaranteed the ship would roll uncomfortably and quickly. But some other factors also played into the decision on how the hull would be shaped.  Even before steel was cut for the first ship, it became apparent that huge numbers of LSTs would be needed during the war. And since existing shipyards were already filled to capacity, new shipyards would have to be built just to build LSTs.  Most of us don’t tend to think of Indiana as a very nautical state, but in fact, almost half of all LSTs would be built in inland shipyards, with the most productive being located in Evansville, IN (right across from Louisville, KY). The Missouri Valley Bridge and Iron Company built a 45 acre yard, and quickly began mass producing the first of what would eventually be 176 LSTs. Several other yards had similar beginnings.

Since these yards had never built ships, and indeed large percentages of their workforces had no construction experience at all, they had to train their workforces from scratch. And of necessity, the ships they built had to be of the simplest possible design practicable. Keeping the design simple, such as having virtually identical framing along almost the whole length of the ship, also simplified production of components. For instance, the design was carefully thought out so that only five different cuts of plate steel were needed in plating over the frame. That meant the fabrication yard could quickly cut the vast numbers of plates needed to speed production. Further, virtually all the government supplied equipment, such as deck fittings, internal fittings, compasses, habitability equipment and whatnot was already standard, and few new items had to be designed, tested or built.  Other steps to speed construction included eliminating camber on the decks. Traditionally, the main deck of a ship has a very slight “arch” to it, with the center of the deck being about 6 inches higher than the sides. This helps speed water draining from the decks. But eliminating this camber greatly eased construction, so simplicity won in that case, and in many others.


LST under construction in Evansville, IN

But just because the Navy was willing to compromise on complexity and accept a simple design, doesn’t mean the LST was crude. It was still a warship, and was built tough. Originally planned to use 1/4” steel for hull plating, instead 3/8” plating was used to add toughness and stiffness. The under the forefoot, where the ship would actually run aground, the plating was a full 1” thick.  Also, the ballast tanking that allowed the ship of change its draught meant the ship had a double bottom, providing strength and improved compartmentation, a valuable consideration for ships likely to face damage.

And the LST was more than a simple hollow shell. While the tank deck  formed the center of the ship, the sidewalls of the ship housed berthing spaces for the ships crew, for the Army (or Marine)  crews of embarked vehicles, galley spaces, shop spaces and storerooms. These sidewall  compartments added further structural strength and great compartmentation.


Click to embiggen

In fact, in spite of the sobriquet “Large Slow Target” only one quarter of one percent of all LSTs were lost to enemy action. 

While yards like the Evansville plant took almost a half a year to build the first ships, beginning in June of 1942, construction times fell rapidly. Four months were needed by 1943. By the end of the war, yards were building LSTs in as little as two months.  Like most mass production programs, getting set up for production took a while, and it wasn’t until much later that large numbers were being brought into service. The lean years of 1943 and 1944 saw commanders in both the Pacific and the European theaters screaming for more LSTs. But by the end of the war, and astonishing 1051 had been built, the vast majority in the last two years of the war.

Getting an LST ashore would seem to be fairly straightforward. Just point the ship at the shore, ring up full speed, and eventually the beach will stop you. And usually, that’s just what happened. But on a lot of very shallow beaches, especially those in Europe, that would still leave the ship quite a way out from the beach.  LSTs would frequently bring along floating causeways to serve as a floating pier between the ship and the shore. Simple rectangular steel boxes, they would be slung from the slab sides of LSTs. As soon as the LST had grounded, they could be cut loose, and moved into position by ships landing craft.

Ships have been running aground from time immemorial. Getting a  ship off a beach was a little more difficult. Obviously, after an LST had discharged its cargo, its reduced displacement would make it easier to float off. US doctrine was to conduct landings at low tide. As the tide came in, the reduced weight and incoming tide was usually enough to refloat the LST. Just in case, LSTs also had a stern anchor and winch. Dropped shortly before the ship ran ashore, the anchor and winch helped retract an LST off the beach. Even though designed to deliver 500 tons of cargo across a beach, it soon became clear that LSTS could be overloaded by 100% and still succe
ssfully beach. And once the cargo was discharged, retracting was no more difficult than if it had landed with the rated 500 tons. The only reason loads even greater weren’t used was that the increased drafts would ground the ship too far out.

As the war in the Pacific ground on, the Marines increasingly favored landing the initial assault infantry waves via amphibious tractors known as LVTs, as opposed to the landing craft we think of from Normandy or countless war movies.  The question was, how do you get LVTs in position to assault the beaches? An LST could carry almost thirty LVTs across vast distances. Upon approaching the objective, rather than trimming their sterns low and bows high, the LST would do the opposite. Trimmed down slightly by the bow, an LST could disgorge a wave of LVTs into the water, where they could form up for their assault upon the beach. Troops from the transports would transfer from LCVPs into the amtracs for the final run into shore. Loaded with 80 pounds of gear, I’d hate to have to clamber from a bobbing 36’ landing craft to a bobbing 30’ floating armored personnel carrier far from shore. It wasn’t the most elegant system, but it worked.


Tank Deck of an LST

The utility of the LST and the large volume of space available lent the design to quite a few modifications and variants. From the very beginning, withdrawing LSTs had been used to remove wounded soldiers from the beachhead. Later, about 30 of them were outfitted with surgical spaces and used as light hospital ships (LST(H)). Unlike regular hospital ships, LST(H) were still combatant ships, and fully combat capable. Most importantly, though, was their ability to rapidly provide critical care to the wounded, almost immediately after an assault began. Wounded troops that might otherwise face considerable delays before significant treatment and evacuation to a hospital ship were instead under the care of surgeons almost instantaneously.

Other LSTs had Quonset huts erected on their main decks, and served as mother ships for small craft, providing office spaces for staffs and headquarters. The vast numbers of landing craft in the Navy imposed a heavy maintenance burden on the fleet. Quite a few LSTs were modified with repair spaces and shops and became Landing Craft Repair Ships (ARL). Other LSTs were used to resupply ammunition to battleships, cruisers and destroyers. The Army used Piper Cubs to spot artillery targets. A handful of LSTs had small flight decks built onto their main decks allowing them to launch the Cubs. Later, the Brodie system, a complex trapeze device, allowed an LST to recover as well as launch Piper Cubs. Later, more extensive conversions, with massive deckhouses, turned a handful into floating self propelled barracks**

Each LST had a crew of about 8 to 10 officers, and up to 130 sailors. A goodly number of the sailors were there primarily to man the self defense anti-aircraft guns on board. Typically, an LST was commanded by a reserve Lieutenant, who likely three or four years before had been a civilian with no naval experience at all. Most sailors had no experience beyond boot camp before reporting aboard their LST shortly before it was commissioned. The amazing transformation of these masses of landlubbers into Old Salts in an incredibly brief span of time is one of the great success stories of WWII.

With the massive demobilization of the Navy after the surrender of Japan, the Navy found itself with hundreds of LSTs on hand, with no use for the vast majority of them. At first, many were used to bring home the millions of soldiers, sailors, airmen and Marines overseas. But as the redeployment home (Operation Magic Carpet) drew to a close, most LSTs were decommissioned, stricken from the Naval Register, and disposed of. Some few were sold and put into service as merchantmen. Others were given or sold to allies. The Navy, of course, kept a handful in service. A fair chunk of the fleet was preserved in mothballs. But for the bulk of the LST fleet, their future lay in the breakers yard, to be converted to razor blades and washing machines.

But that’s not the end of the LST story, just yet. When North Korean forces steamrolled over the South Koreans and Americans in 1950, General Douglas McArthur’s bold plan for an amphibious landing at Inchon meant the call went out for LSTs. The Navy actually had to bring back into service several that had been transferred to Japanese control to provide logistical services to SCAJAP- the Supreme Commander, Allied Powers, Japan. Operated by Japanese merchant crews, they had been plying the waters of the Land of the Rising Sun. They were quickly brought back into US service.

With the utility of amphibious shipping again established, the Navy also built small numbers of follow-on versions of the LST. Steam power was used for some. Some WWII era LSTs were brought out of mothballs. The wide open main deck of the LST also invited the use of the newly developed helicopter. With helicopters and small boats, some LSTs were used to support mine warfare. The helicopters could spot mines in shallow water, and small boats could sweep them without risking larger vessels.

WWII built LSTs would continue to serve with the Navy in small numbers through the Vietnam War, but eventually they succumbed to the strains of old age and progress. Newer, larger, more versatile types replaced the LST in service. A handful still survive. One, modified to serve as a car ferry today still plies coastal waters. Another, LST-325, served for many, many years in the Greek Navy, but was gifted to serve as a museum ship here in America. Transferred in 2001, after an arduous voyage, it became the centerpiece of an LST museum in Evansville, IN.


*The Navy would struggle another 20 years to find a faster hull for LSTs, and in the end, would have to build a class of LSTs with more conventional hull lines, and discharging their vehicles over the bow via an enormous ramp. What goes around comes around. But this LST-1179 (Newport County) class ships weren’t terribly successful, nor cheap. While they served full careers, they weren’t replaced at the end of their lives.

**These self propelled barracks ships would be put to extensive use in Vietnam. More on that later.

Note: Readers interested in a more comprehensive design history of the LST are encouraged to turn to Norman Friedman’s US Amphibious Ships and Craft.

PS. The British connection is more important than my brief post has conveyed. The LST was hardly the only vessel or concept inspired by them. The Landing Ship Dock was another avenue they developed to provide armor support to the initial waves of a landing. The LSD had a massive well deck that was home to large numbers of large landing craft. By flooding the well deck, landing craft pre-loaded with tanks could be floated out. This avoided the need to swing tanks onto landing craft via precarious booms. Later classes of the LSD serve to this day.

PPS. As large as the LSTs were, and they were commissioned warships, they went to war bearing humble names. Their only name was their hull number. But surviving LSTs starting about 1955 were graced with real names. Each was named after a county, for instance, USS Lincoln County was originally named USS LST-898.

9 thoughts on “The Large Slow Target”

  1. Thanks for this post. My Dad was a BM2. He picked up his ship LST-649 in Seneca, IL. sailed her down the river, thru the canal and spent the duration of the war in the So. Pacific.
    Found the above site some years ago and he is in the crew picture taken 60+ years ago. Amazing.
    I toured the LST-325, the one you mentioned that was restored in Greece and sailed back to the States. It was visiting the MMA in Buzzards Bay, MA. around 2004. Iron men to sail that across the Atlantic. The Greatest Generation is a fitting name for those who took them to war.

  2. Superb post! The LST is one of the marvels of modern warfare. I will be writing about the little cousin of the Large Slow Target, the Landing Craft, Tank (LCT), when I can get the time (and have finished the not-unrelated OMFTS piece).

    1. Don’t forget that the LCT MK5 was redesigned into the drive through LCT MK6 by Manitowoc Shipbuilding, makers of the highest quality subs of the USN during the War. Zounds, but Badgers are useful creatures!

      I believe that the first container ship was a surplus LST, as was the first deepwater oil drilling rig. LSTs were sort of the Vice-Grips in the gator’s toolbox. A very well written post, Brad! I am in the process of moving, and spent part of the weekend reading Friedman’s US Amphibians.

    2. Cap’n Fatso is a great book. Very funny. Almost as good as Stand By to Start Engines. If Interlibrary loan can’t help, I’d loan, repeat loan, you my copy.

  3. Great Post, but a couple of minor points.

    1. The LST stern anchor had another reason that was probably even more important than aiding in getting the ship off the beach. It kept the ship from broaching in the surf. Immediately after landing, the stern is afloat while the bow is aground and the ships engines and rudders have limited utility to keep the ship straight. The wind and surf will try to push the ship broadside to the beach. The stern anchor, and ballasting the ship down once beached, prevents this as well as making retraction easier.

    2. The genesis of the LSD (and the bow ramp for landing craft for that matter) actually came from the Japanese Army, whose LSDesque ship, the Shinsu-maru was completed in 1935 and first observed by US and UK naval personnel in 1937 off Shanghai.

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