High-speed transport

High-speed transports were converted destroyers and destroyer escorts used in US Navy amphibious operations in World War II and afterward. They received the US Hull classification symbol APD; "AP" for transport and "D" for destroyer. In 1969, the remaining ships were reclassified as "Fast Amphibious Transports", hull symbol LPR.

APDs were intended to deliver small units such as Marine Raiders, Underwater Demolition Teams, and United States Army Rangers onto hostile shores. An APD could carry up to 200 troops - a company-size unit - and approximately 40 tons of cargo. It could also provide gunfire support if needed. USS Manley was officially designated the Navy's first high-speed transport on 2 August 1940 when she became APD-1.

Before the United States entered World War II, as newer and more modern destroyers joined the fleet, some older destroyers were refitted for other duties: as seaplane tenders, destroyer minelayers, or destroyer minesweepers, and in an innovation, as fast transports carrying fully equipped troops for assault landings.^{[citation needed]} During the war, newly built or unfinished destroyer escorts were converted to APDs.

The first group of APDs (APD-1 through APD-36) were converted from one Caldwell-class, 17 Wickes-class, and 14 Clemson-class "flush-deck" destroyers built during and after World War I. Some of these had been previously converted to aircraft tenders or other uses.

In the conversion, the two forward boilers (out of four) were removed along with their smokestacks (reducing speed to 25 knots (46 km/h)). Accommodation for 200 troops was installed in the former engine spaces. The original armament of four 4"/50 low-angle guns, one 3"/23 anti-aircraft gun, and twelve 21-inch torpedo tubes was replaced with three modern 3"/50 dual-purpose guns, one 40 mm AA gun, and five 20 mm AA guns. Two depth charge racks and up to six K-gun depth charge throwers were carried. In place of the torpedo mounts, four davit-mounted LCPLs (Landing Craft Personnel, Large) were shipped. Later, the LCPLs were replaced by a version with a bow ramp, the LCPR (Landing Craft Personnel, Ramped).

The second group of APDs were converted from 43 Buckley-class destroyer escorts (DE)s built in 1943-1945. Two further planned conversions were canceled at the end of the war. These converted vessels were known as the Charles Lawrence class.

In the conversion, the superstructure was expanded to provide accommodation for 162 troops. The original gun armament of three 3"/50 DP guns and two 40 mm AA guns in a twin mount was replaced with one 5"/38 DP gun and six 40 mm AA guns in three twin mounts. The original six 20mm AA guns were retained. The Charles Lawrence class also had two depth charge racks and up to eight K-guns. Typically, the converted DEs carried four LCVPs (Landing Craft Vehicle and Personnel) in a stacked davit configuration.

The third group of APDs were converted from 51 Rudderow-class destroyer escorts built in 1943-1945. All but one of these were converted while under construction. These converted vessels were known as the Crosley class.