Well, try 18,000 troops in one division at Tarawa not 60,000. in two divisions. Of these 18,000, 1/3 were not used the first day because they were Corps reserve. First day about 6,000 troops had been put ashore minus casualties vs. @5000 Japanese. Not exactly the situation as you described it. Doctrine, tactics and techniques had been refined (and were by the experience gained on each landing) but were still basically those developed by the US during the interwar years. The biggest changes were technological and the greatest contribution by the British was in specialized craft (technical as you termed it) of which the LST is the most notable. The British built the first example, the US refined the design and both US and British versions were built by their respective countries. Many US versions were supplied to the British. The LCI a joint US/UK development, the UK proposed a disposable vessel with no sleeping accommodations for cross channel applications, the US Navy pushed for a more ocean going design which was adopted and built in the US. The amphibious workhorses for the Americans, the Higgins boat, had been adopted in various iterations since 1937. The LCP(L) was even provided to the British in 1940 for cross channel raids. The LCP(R) incorporated a ramp, the idea for which came from observations of the Japanese Daihatsu and was further refined by making it full width to become the LCVP. The only assistance received from the British on this whole line of development was in helping decide on which version to adopt. The US Marine Corps and the Navy amphibious pioneers wanted the 36' version, the Navy bureau the 32' version because it would not require relocation of their boat davits on ships. The Admiralty when visiting Higgins industries expressed a preference for the 36' boat so the Navy bureau in the interests of commonality agreed to the standardize on the 36' version. The US LCM was an enlarged Higgins boat ordered to obtain better seakeeping characteristics than those in the Bureau designed tank lighter, a craft in service since the late '30's. Dieppe is in no way comparable to the two operations you mentioned, about half the troops and it was a cross channel operation, not nearly as complicated as the fleet operations necessary to project and support a force across thousands of miles. It's like comparing apples and oranges. As for Tarawa, there were many valuable lessons to be learned and applied to all subsequent amphibious landings. Tarawa was the first assault against a heavily fortified objective. First, while the Navy had a small, experimental unit formed in 1942 called the Navy Scouts and Raiders that had participated in the Torch landings. It was the obstacles encountered at Tarawa that caused Admiral King to commit the resources and personnel to expand them and form the Naval Combat Demolitions Units. In fact UDT's were heavily used two months later during the Marshall's invasion. These UDT's provided invaluable service during many invasions post-Tarawa including Normandy. Naval and air bombardment TTP was modified to incorporate lessons learned including better coordination with the landing forces and point vs area targeting. Communications procedures and equipment assets were upgraded and refined. It was incorporation of the Tarawa lessons that allowed the Marshall's to be seized at relatively low cost. If these improvements we adopted within two months, you can't say they had no effect on the later operation 7-8 months later. Well, the obstacles you mention were encountered in the Pacific, at Tarawa in fact. The reason they decided to hit the north shore was it was the least heavily fortified, the mines, anti-boat and anti-vehicle obstacles on the other sides were numerous and well emplaced, the reef was determined to be the lesser evil. In fact tracs that tried to land troops on Ryan's green beach were destroyed by mines. Ryan had seized enough of that end of the island that troops were landed by rubber boat to avoid the mines. LVT's and landing boats would have been destroyed had that been a primary beach. Tank traps were encountered on numerous landings. But to answer your first points. This is a recurrent theme on this board. Why didn't:- - The US Marines play a bigger part on D Day-They weren't needed. The US Army and British had plenty of experience in amphibious landings and amphibiously capable divisions. The Navy amphibious personnel in the ETO had a great deal of real life experience as well. Besides, the Marines were needed in the Pacific and there weren't enough to go around. - Op Overlord follow the American methiods developed in the Pacific-The allied leaders incorporated all lessons learned from each and every operation, regardless of theater. They used all applicable methods. Pacific landings, Med landings, European landings, previous experience was applied. - Use the LVT-amply explained by numerous posters, whatever limited advantages might have been enjoyed were far outweighed by the negatives.