When you mention the words “amphibious warfare” most people think immediately of the US Marines, and rightly so. But during WWII, the Army invested huge resources into the ability to land on a hostile shore and conduct operations.
There are two general types of amphibious operations: ship-to-shore and shore-to-shore. Ship to shore operations are those in which the landing force is transported to the objective in large, ocean going vessels, then landed via small craft onto the shore. Shore to shore operations take place over relatively short distances, and generally the troops are carried in smaller craft, rather than large transports. Obviously, the anticipated objectives will dictate which approach is taken.
In the late 1930s, with war clouds clearly on the horizon, both the Army and the Marines came to the conclusion that they would need to develop a serious amphibious capability, but they reached different conclusions because of very different assumptions about what type of war they would be fighting.
For 20 years, the Navy had forseen war with Japan in the Pacific. And the cornerstone of the Navy’s strategy to defeat Japan was to defeat the Japanese fleet in a battle, likely somewhere near the Philipines. Since it would be impractical for the fleet to steam all the way from San Diego or Pearl Harbor and fight in those waters, the need for advanced bases was clear. And the Marines understood that as a consequence of the Washington Naval Treaty of 1922, any islands that could serve as an advance base would almost certainly be held by the Japanese. That meant the Marines had to be ready to travel the huge distances of the Pacific, land on remote islands, and seize relatively small objectives. For the Marines, this was a raison de etre.
The Army faced a different challenge. The Army had no desire to get into the amphibious warfare business. But watching the rise of Nazi German power, the Army leadership was convinced that sooner or later, they’d have to go fight in Western Europe again. And, unlike 1918, they weren’t at all sure the French ports would be available to land the huge armies planned. After the fall of France in June of 1940, the cold realization came that just to get the Army to the fight would mean sooner or later, landing somewhere in Western Europe, under the guns of the enemy. And not only would the Army have to land there, they would have to build up their forces and simultaneously supply them over the beaches until a suitable port could be seized. Fortunately for the Army, England was still available as an advance base.
The Army didn’t completely ignore the ship to shore model of amphibious warfare, mostly because they couldn’t. When it became apparent that no cross-Channel operation to invade Europe would be possible in 1942 (mostly because of a lack of landing craft) President Roosevelt made the decision that a front in the Atlantic theater would be opened in North Africa. A combined British and American force would be landed in the French occupied territories of North Africa, then drive east to engage the German forces in Tunisia. Due to the distances involved, this could only be a ship to shore movement. Many forces sailed from England, but a significant portion sailed all the way from ports on the East Coast of the US. Even against only fitful French and German resistance, the invasion fleet lost five large transports. One of the lessons the Army learned was that transports waiting to discharge their troops and cargoes were extremely vulnerable. In response, the Army wanted to make sure as many ships as possible had the ability to beach themselves to unload, minimizing the reliance on small craft such as the Higgins boat, LCVP, and the LCM.
These craft were carried near the objective by transports, and lowered over the side by booms or davits. That took time, time during which the transports, only 5-10 miles offshore, were vulnerable to submarines, airplanes and even coastal artillery. While they were fairly good for getting the first units of lightly armed troops ashore, they were less efficient at getting ashore the huge numbers of follow-on troops needed, and importantly, the massive numbers of vehicles the troops would need to break out from any beachhead. Further, they just weren’t capable of bringing ashore the cargoes of supplies, fuel and ammunition the troops would need. Something bigger was needed. And the first of these bigger craft was known as the LCT, or Landing Craft Tank. An LCM3 could carry one tank, barely. An LCT was a much bigger craft and could carry from 3 to 5 tanks. Five was an optimum number, as that was the number of tanks in a platoon, and keeping tactical units together on a landing greatly assisted in the assualt. As you can see from the picture, the LCT was essentially a self-propelled barge with a bow-ramp.
The LCT could easily sail from England to France, or from Mediterranean ports in North Africa to Sicily and Italy. And while it could carry real numbers of tanks, something even better was in the works- the Landing Ship Tank, or LST. Early in the war, espcially as the Allies were first gearing up for the invasion of North Africa, the Army (and especially the British) realized they had no way of shipping tanks overseas and landing them across beaches in any numbers. The LCT couldn’t handle the voyage, and loading LCMs over the side of a transport was problematic in anything but a flat calm. Worse, tanks kept getting heavier and heavier, faster than the booms on transport ships could grow to handle them. The idea arose of converting vessels originally built to carry rail cars from Florida to Panama as tank carriers. But while they could drive the tanks on at the embarkation point, the problem of discharging them remained. To unload them, the Army would need to seize a port. Indeed, this limitation was precisley why Casablanca was a target of the invasion. Enter the British. They had built a series of very shallow draft tankers to serve the waters around Venezuala. The reasoned that the design could quickly be adapted to build a large vessel that could safely beach itself, unload tanks held in what had formerly been the holds via a ramp in the bow, and then retract itself from the beach. Unlike an LCT, the LST might be ungainly and slow, but it was a real seagoing vessel.
While the LST was very valuable in bringing tanks, up to 20 at a time, it turns out the real value was in trucks. The Army in WWII was by far the most mechanized and motorized army in the world. And that meant trucks. Lots of trucks- to move people, supplies, tow guns, you name it. And the LST could carry a lot of trucks, already loaded, both on its tank deck, and on the topsides. And unlike the hassle of unloading a regular transport, all they had to do was drive down a ramp. After making an initial assault, as soon as an LST had discharged its tanks, it would turn around, go back to England (or where ever) and load up on trucks to build up the forces on the beachhead. To say the LST was a success would be a bit of an understatement. The US built roughly 1100 of them during the war for our Navy and the British.
While the LST was great for carrying tanks and trucks, it didn’t do so well at carrying people. One thing the Army really wanted was a small ship that could carry a rifle company from England and land them on the shores of France, non-stop and as a unit. The trick was getting the size just right. It had to be small enough to be built in large numbers, but big enough to cross the Atlantic on its own. It wouldn’t be expected to carry troops across the Atlantic. Those would come across on troopships. But any vessel large enough to do the job would be too large to carry aboard a transport. Pretty soon, the Navy designed and built the Landing Craft Infantry, or LCI. This was a vessel designed almost entirely with the invasion of Normandy in mind. It carried about 200 troops, roughly a reinforced rifle company, for up to 48 hours, which is about the time it took to load and transport them from ports in the Southwest of England and discharge them over the beaches of Normandy.
The Army had one other great tool for bringing supplies across the beach. In the days before the LST was available, the only method of getting trucks ashore across the beach was to winch them over the side of a transport into an LCM. Someone at GM had the bright idea of doing away with the LCM part, and making the truck amphibious. That way, the truck could swim ashore, then drive inland to the supply dumps. The result was basically a boat hull grafted onto a 2-1/2 ton truck, known as the DUKW, and commonly called a “duck.” Thousands of DUKWs, almost all manned by African American soldiers, brought wave after wave of critical supplies ashore across the beaches of Normandy and at other beaches the Army invaded. Unlike most landing craft, these were bought by, and operated by the Army, not the Navy.
Finally, in the Pacific, when you speak of amphibious warfare, again, you rightly think of the Marines. But in fact, the Army had a huge presence there as well. Indeed, it was always a larger prescence than the Marines. The Army made over 100 amphibious assualts in the Pacific theater, many in the Southwest Pacific in and around New Guinea. In conjunction with the US Seventh Fleet, MacArthur’s forces in the Southwest Pacific became masters at the art of amphibious warfare, striking where the Japanese least expected them, and routinely conducting sweeping flanking movements that left Japanese garrisons cut off and useless. Dan Barbey, the Commander of 7th Fleet became known as “Uncle Dan The Amphibious Man.” All this with a fleet mostly composed of tiny LCTs, a few LSTs and LCIs.
The Army also fought alongside the Marine Corps in some of their most storied battles, such as the invasions of Saipan and Okinawa. Indeed, if the atomic bomb attacks had not lead to the early surrender of Japan, the invasion of the home islands would have been mostly an Army affair. Largely as a result of the Army’s preocupation with the European theater, these magnificent efforts have received little attention from the public at large.
After WWII, the Army’s focus again turned to Europe and the Cold War. For several reasons, including the vulnerability of shipping to nuclear weapons, amphibious operations fell out of favor with the Army. The Marines of course, continued to maintain that unique capabilty. Currently, the Army has no capability to conduct a landing against opposition. Current doctrine does still provide for limited ability to sustain forces by what is known as LOTS or “Logistics Over The Shore” and for the rapid deployment of troop units to hot spots via Afloat Prepositioning Squadrons. Basically, sets of unit equipment are mainained aboard large ships just days sailing from their possible objectives. If needed, they can sail to a friendly port or harbor, and unload their cargoes to meet up with troops flown in by either commercial aircraft or military transport planes. Alternatively, they can serve as a follow-on force to reinforce a beach seized by Marine amphibious assault.