The hull of the LCI(L) was relatively long and narrow. The deck was wider than the prow and two gangways either side gave onto a pair of ramps that could be lowered down onto the beach. The troops would dismbark down these. The steepness and narrowness of the ramps would have made the LCI impractical for landing troops as part of an initial assault against a defended beach and they were reserved for the follow up waves. The first LCI (L)s entered service in 1943 chiefly with the Royal Navy (RN) and U.S. Navy. Early models were capable of carrying 180 troops, this was raised to 210 later. Craft in service with the two navies had some variation according to national preferences. Some 923 LCI were built in 10 American yards and 211 provided under lend-lease to the Royal Navy. In Royal Navy service they were known as "HM LCI(L)-(pennant number)". In 1945, 25 were provided by the United States to the Soviet Union.
Most LCI(L)s were struck from service by both the RN and the USN in 1946. In February 1949, the U.S. reclassified the remaining LCIs as "Landing Ship Infantry" (LSI). Landing Ship Infantry was a term that had been used during the war since around 1941 by the British for various vessels such as converted ferries and passenger ships that could carry 800–1,800 troops close to shore, the final transfer being by smaller boats.
At the same time as the LCI(L) was handed over for US development and production, the British reworked their need for a raiding vessel into something that could be produced natively without making demands of limited resources. Fairmile Marine had already designed a number of small military vessels that were built in wood and they produced the Fairmile Type H which was another prefabricated wooden design. This was taken on as the "Landing Craft Infantry (Small)" or LCI(S).
The LCI(G) variant was used for the basis of the LCS(L) class of Landing Craft Support ships. The same hull was used and more armament was added, but the troop carrying capability was removed.
The Landing Craft Support (Large) or "LCS (L) Mark 2" was the same vessel as the LCI(S) but intended for use as a support vessel to provide firepower alongside other landing craft and was not to being beach but carried extra armament. The LCS(L) Mark 1 had carried a tank turret complete with its QF 2 pounder gun but for the Mark 2 this was replaced with a tank turret mounting the QF 6 pounder gun. To this was added two oerlikon 20 mm cannon and two 0.5 inch Vickers machine guns. Ten were built in all.