Landing craft
Eight weeks later the craft was doing trials on the River Clyde. All landing craft designs must find a compromise between two divergent priorities; the qualities that make a good sea boat are opposite to those that make a craft suitable for beaching. The craft had a hull built of double-diagonal mahogany planking. The sides were plated with "10lb. DIHT" armour, a heat treated steel based on D1 steel, in this case Hadfield's Resista 1⁄4.
The Landing Craft Assault remained the most common British and Commonwealth landing craft of World War II, and the humblest vessel admitted to the books of the Royal Navy on D-Day. Prior to July 1942, these craft were referred to as "Assault Landing Craft" (ALC), but "Landing Craft; Assault" (LCA) was used thereafter to conform with the joint US-UK nomenclature system.: 10 

The Landing Craft Infantry was a stepped up amphibious assault ship, developed in response to a British request for a vessel capable of carrying and landing substantially more troops than the smaller Landing Craft Assault (LCA). The result was a small steel ship that could land 200 troops, traveling from rear bases on its own bottom at a speed of up to 15 knots (28 km/h; 17 mph). The original British design was envisioned as being a "one time use" vessel which would simply ferry the troops across the English Channel, and were considered an expendable vessel. As such, no troop sleeping accommodations were placed in the original design. This was changed shortly after initial use of these ships, when it was discovered that many missions would require overnight accommodations.
The first LCI(L)s entered service in 1943 chiefly with the Royal Navy (RN) and United States Navy. Some 923 LCI were built in ten American shipyards and 211 provided under lend-lease to the Royal Navy.

Specialized vehicle landing craft: Following the Inter-Service Training and Development Centre 's (ISTDC) successful development of the infantry carrying LCA, attention turned to the means of efficiently delivering a tank to a beach in 1938. Enquiries were made of the army as to the heaviest tank that might be employed in a landing operation. The army wanted to be able to land a 12-ton tank, but the ISTDC, anticipating weight increases in future tank models specified 16 tons burthen for Mechanised Landing Craft designs. Another limit on any design was the need to land tanks and other vehicles in less than approximately 2+1⁄2 ft of water (0.76 m).
Design work began at John I. Thornycroft Ltd. in May 1938 with trials completing in February 1940. Constructed of steel and selectively clad with armour plate, this shallow-draft, barge-like boat with a crew of 6, could ferry a tank of 16 long tons to shore at 7 knots (13 km/h). Depending on the weight of the tank to be transported the craft might be lowered into the water by its davits already loaded or could have the tank placed in it after being lowered into the water.

Although the Royal Navy had the Landing Craft Mechanised at its disposal, in 1940 Prime Minister Winston Churchill demanded an amphibious vessel capable of landing at least three 36-ton heavy tanks directly onto a beach, able to sustain itself at sea for at least a week, and inexpensive and easy to build. Admiral Maund, Director of the Inter-Service Training and Development Centre (which had developed the Landing Craft Assault), gave the job to naval architect Sir Roland Baker, who within three days completed initial drawings for a 152-foot (46 m) landing craft with a 29-foot (8.8 m) beam and a shallow draft. Ship builders Fairfields and John Brown agreed to work out details for the design under the guidance of the Admiralty Experimental Works at Haslar. Tank tests with models soon determined the characteristics of the craft, indicating that it would make 10 knots (19 km/h; 12 mph) on engines delivering about 700 hp (520 kW). Designated the LCT Mark 1, 20 were ordered in July 1940 and a further 10 in October 1940.
The first LCT Mark 1 was launched by Hawthorn Leslie in November 1940. It was an all-welded 372-ton steel-hulled vessel that drew only 3 feet (0.91 m) of water at the bow. Sea trials soon proved the Mark 1 to be difficult to handle and almost unmanageable in some sea conditions. The designers set about correcting the faults of the Mark 1 in the LCT Mark 2. It was longer and wider, with 15-and-20-pound (6.8 and 9.1 kg) armoured shielding added to the wheelhouse and gun tubs.

The Mark 3 had an additional 32-foot (9.8 m) midsection that gave it a length of 192 feet (59 m) and a displacement of 640 tons. Even with this extra weight, the vessel was slightly faster than the Mark 1. The Mk.3 was accepted on 8 April 1941. The Mark 4 was slightly shorter and lighter than the Mk.3, but had a much wider beam (38 ft 9 in (11.81 m)) and was intended for cross channel operations as opposed to seagoing use. When tested in early assault operations, like the ill-fated Allied raid on Dieppe in 1942, the lack of manoeuvring ability led to the preference for a shorter overall length in future variants, most of which were built in the United States.
When the United States entered the war in December 1941, the U.S. Navy had no amphibious vessels at all, and found itself obliged to consider British designs already in existence. One of these, advanced by K.C. Barnaby of Thornycroft, was for a double-ended LCT to work with landing ships. The Bureau of Ships quickly set about drawing up plans for landing craft based on Barnaby's suggestions, although with only one ramp. The result, in early 1942, was the LCT Mark 5, a 117-foot (36 m) craft that could accommodate five 30-ton or four 40-ton tanks or 150 tons of cargo. This 286-ton landing craft could be shipped to combat areas in three separate water-tight sections aboard a cargo ship or carried pre-assembled on the flat deck of a Landing Ship, Tank (LST). The Mk.5 would be launched by heeling the LST on its beam to let the craft slide off its chocks into the sea, or cargo ships could lower each of the three sections into the sea where they were joined together.

Development of Landing Ships: A further development was the Landing Ship, Tank designation, built to support amphibious operations by carrying significant quantities of vehicles, cargo, and landing troops directly onto an unimproved shore. The British evacuation from Dunkirk in 1940 demonstrated to the Admiralty that the Allies needed relatively large, ocean-going ships capable of shore-to-shore delivery of tanks and other vehicles in amphibious assaults upon the continent of Europe. The first purpose-built LST design was HMS Boxer. To carry 13 Churchill infantry tanks, 27 vehicles and nearly 200 men (in addition to the crew) at a speed of 18 knots, it could not have the shallow draught that would have made for easy unloading. As a result, each of the three (Boxer, Bruiser, and Thruster) ordered in March 1941 had a very long ramp stowed behind the bow doors.
In November 1941, a small delegation from the British Admiralty arrived in the United States to pool ideas with the United States Navy's Bureau of Ships with regard to development of ships and also including the possibility of building further Boxers in the US. During this meeting, it was decided that the Bureau of Ships would design these vessels. The LST(2) design incorporated elements of the first British LCTs from their designer, Sir Rowland Baker, who was part of the British delegation. This included sufficient buoyancy in the ships' sidewalls that they would float even with the tank deck flooded. The LST(2) gave up the speed of HMS Boxer at only 10 knots but had a similar load while drawing only 3 feet forward when beaching.
Congress provided the authority for the construction of LSTs along with a host of other auxiliaries, destroyer escorts, and assorted landing craft. The enormous building program quickly gathered momentum. Such a high priority was assigned to the construction of LSTs that the previously laid keel of an aircraft carrier was hastily removed to make room for several LSTs to be built in her place. The keel of the first LST was laid down on 10 June 1942 at Newport News, Va., and the first standardized LSTs were floated out of their building dock in October. Twenty-three were in commission by the end of 1942. Lightly armored, they could steam cross the ocean with a full load on their own power, carrying infantry, tanks and supplies directly onto the beaches. Together with 2,000 other landing craft, the LSTs gave the troops a protected, quick way to make combat landings, beginning in summer 1943.