From 1941 Coast Guard crews had served successfully on board Navy attack transports (APs & APAs) and with personnel to spare, it was an obvious choice to let the Coast Guard continue to assist in manning various ships of the ever-increasing Navy fleet. Their experience in operating in all types of surf conditions as well as on the high seas made the Coast Guard crews a valuable addition to the Allied invasion fleets. They readily took to all of the various types of landing craft utilized by the Navy, including the Landing Craft Infantry, Large, or LCI(L)s, beginning in 1943

Even though these vessels had Coast Guard crews all LCI(L)s remained commissioned US Navy vessels. The Coast Guard manned 28 of these landing ships that despite their name were anything but "large." Coast Guard-manned LCI(L)s participated in almost all of the major amphibious invasions undertaken by the US during the war. Twenty-four were grouped into a single flotilla which was commanded by a Coast Guard officer, Commander Miles Imlay, USCG. First known as Flotilla 4 for the invasion of Sicily and Salerno, its designation was changed to Flotilla 10 for Operation Overlord, or the invasion of Normandy. They were reinforced with 12 Navy-manned LCIs, making the Flotilla's total number of landing craft 36, divided evenly between the invasions at Omaha and Utah beaches. It was at Omaha Beach that the flotilla suffered grevious losses, including four LCI(L)s completely destroyed by enemy fire and a number of others damaged. The surviving vessels performed yeoman duties in the English Channel for the next several months before sailing back across the Atlantic, now under the command of Commander Aden C. Unger, USCG.

Once back in the U.S., the flotilla's four lost LCIs were replaced with LCI(L)s 520, 562, 581, and 583. Many of the veteran crews were replaced with new recruits and officers and they underwent amphibious training in the Chesapeake. The flotilla, now designated as Flotilla 35, then sailed to the San Diego in preparation for service in the Pacific Theatre. Once in San Diego, they served as training ships while awaiting assignment to the Western Pacific, where many participated in the campaigns in the Philippines and Okinawa, among others.

The LCI(L)s carried out a myriad of duties while in the Pacific. These included: minesweeping, serving as ferries for passengers and mail, made smoke to screen US Navy capital warships during invasion bombardments, fought off kamikaze attacks, trained B-29 crews in ditching techniques, laid buoys and carried out other aids to navigation work, escorted submarines, conducted air-sea rescue patrol duty, operated as harbor entrance control vessels, and acted as salvage vessels. Many participated in the mine-clearing operation in the East China Sea known as "Operation Klondike" after the Japanese surrender. A kamikaze hit and damaged LCI(L)-90 while participating in the invasion of Okinawa. She was repaired and returned to service.

They also worked in Japanese waters after the end of the war, visiting various Japanese ports. They then returned to the United States in late 1945 and early 1946. All were all decommissioned in March, 1946.