Experience in the "Evacuation of Dunkirk" of 1940, which saw tens of thousands of men saved from capture or death at the hands of the advancing Germans, led the British to seek a more streamlined "ship-to-shore" process. This endeavor, helped along by American factories, eventually resulted in a plethora of amphibious assault support vessels that went on to include the "Landing Ship, Tank" (LST) - for moving armor from staging point to shore - and the "Landing Ship, Infantry" (LSI) - for the same purpose though involving ferrying infantry personnel directly to shore lines. Like the LST, the LSI family eventually included variants of the basic ship concept and, collectively, these vessels proved supremely critical to Allied operations from 1943 onward.
United States factories pumped out hundreds of British-originated amphibious assault-related warships and boats during the war. Parties involved included the Brown Shipbuilding, Commercial Ironworks, Consolidated Steel Corporation, Defoe Shipbuilding Company, Federal Shipbuilding & Drydock Company, New Jersey Shipbuilding, and New York Shipbuilding among others. Operators beyond the United States and Britain included Canada, France (Free French forces), the Republic of China Navy, and the Soviet Union (via Lend-Lease). 923 examples were delivered from 1942 until the end of the war in 1945 and these primarily served from 1943 until 1946.
The original vessel design was envisioned as something of a "disposable" battlefield system, ferrying troops across the English Channel and delivering them to awaiting beaches. From then on, the vessels would be abandoned, most likely left for the scrap heap. As such, there was little in the way of creature comforts for the infantry it ferried - simple benches added for seating during the voyage. In all, the hold would carry some 180 combat-ready personnel for up to two days journey time - the total was eventually increased to 210 before the end of the war.
The resulting steel-hulled, 246-ton design featured two banks of Detroit Diesel 6051 "Quad" series engines developing 1,600 horsepower to 2 x shafts - this was essentially eight General Motors truck diesels coupled together for maximum power utilizing an existing powerplant system. This propelled the relatively fast vessel at speeds nearing 16 knots out to ranges of 4,000 nautical miles. Dimensions included a length of 158.5 feet, a beam of 23.2 feet, and a draught of 6 feet. The shallow draught was of note for the vessel was to hold deep water capabilities when crossing the Channel and then manage shallower water sources the closer it came to shore. The operating crew numbered twenty-four and armament was 4 x 20mm Oerlikon cannons (sometimes five) for local anti-aircraft protection. Early-form ships forced troops to debark by way of catwalks and ramps while later versions (from LCI(L)-351 onwards) added the bow door / ramp combination which proved equally effective in the LST models for unloading vehicles.
The vessels were officially named "Landing Craft, Infantry (Large)" (LCI(L)) and offered more passenger-hauling capability than the then-presently-used British Landing Craft Assault (LCA) ships. Three versions of the basic concept was delivered - one with a squared-off conning tower, another with a rounded conning tower design and side-mounted ramps, and the third with a rounded conning tower and bow-mounted ramp.
Variants of these went on to include: the LC(FF) Flotilla Flagship which was developed to ferry flag officers, staff, and crew; the LCI(G) Gunboat which carried 3 x 40mm Bofors AA guns, up to 6 x 0.50 caliber heavy machine guns, and 10 x Mk 7 rocket launchers for supporting amphibious operations at range; LCI(M) Mortar as a mortar carrier seating 3 x 4.2" M2 mortars for ship-to-shore bombardment; LCI(R) Rocket was similar in scope but carried 6 x 5" rocket launchers instead.
The LCI(S) was a British-produced development made specifically for local manufacture - known as the "Landing Craft Infantry (Small)" - and relied on wood construction by Fairmile with Hall-Scott gasoline engines. The LCS(L) was also locally-built in Britain and operated as support vessels with increased armament but only ten of these were constructed. The LCS(L) Mk III / LSSL was the Landing Craft Support (Large) model built by the United States as gun platforms - one hundred thirty of this form appeared before the end of the war.
LCI(L) vessels were first used during the Allied invasion of Sicily in July of 1943 and their value was such that they headlined all future amphibious assault operations throughout the rest of the war. The vessels were used in the famous "D-Day" invasion landings of Normandy the following year (June 1944) in which the British fielded 130 such ships while the Americans brought along 118 during the beach assault. At least thirty were constructed for the Soviet Union and eight were delivered to Free French forces. The importance of these landing ships in the war could not be overlooked - they were used in every major theater of the war and proved so crucial in the retaking of North Africa, Europe, and the Pacific that, in many ways, they stood as the true movers and shakers of the Grand War - as valuable as any one aircraft, tank, or gun fielded in the conflict.