High speed transport
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High Speed Transports were converted destroyers used to support amphibious operations in World War II and afterward. They received the US Hull classification symbol APD; "AP" for transport and "D" for destroyer.
APDs were intended to deliver small units such as Marine Raiders, UDT teams and Army Ranger units onto hostile shores. They could carry up to a company size unit. They were also capable of standing off shore and providing gunfire support as needed. The earliest APDs were World War I vintage flush-deck destroyers. These ships had two boilers and their stacks along with all of their torpedo tubes removed during conversion to APDs. These were replaced by four LCPL landing craft, their handling machinery and troop stowage and quarters. Because of the kamikaze threat being encountered, the fast transports were relatively well armed; 3 inch/50 guns replacing her original 4 inch/50 guns, single Bofors 40 mm guns aft along with five 20 mm anti-aircraft guns. To offset these additions four depth charge throwers and a single depth charge stern rack were removed. The later APDs were newly constructed Destroyer escorts (DE). These ships were converted to High-speed Transports by increasing troop berthing and equipment storage amidships, adding four LCVPs and a boom crane aft. All APDs in the Navy inventory on 1 January 1969 were redesignated as (LPR).
[edit] Conversion and Use in WWII
As newer and more modern destroyers began joining the fleet some of the old ships were assigned to other duties such as tending seaplanes, laying or sweeping mines, or for a newer innovation in modern warfare, carrying fully equipped troops for assault landings as fast transports.
The exigencies of the campaign for Guadalcanal, where neither side enjoyed the overwhelming local naval and air supremacy which insured victory in every other amphibious operation of the war, necessitated an increase in the number of high-speed transports, hybrid warships which combined the functions of transports and destroyers into one. The concept of the high-speed transport embodied sufficient armament for the ship to defend herself against smaller warships and to support the troops she carried with sufficient speed to enable her to outrun more heavily armed ships.
During the modifications forward funnels were removed as the forward boiler and fire rooms were converted to accommodate troops, and the torpedo tubes came off to accommodate four sets of davits and four 36-foot landing craft to put her embarked troops ashore. Though the ships retained a four-gun main battery configuration, the obsolete single purpose 4-inch guns were swapped for more up-to-date dual-purpose 3-inch/50 calibre guns and antiaircraft defenses were further augmented by the addition of several single 20-millimeter Oerlikons and .50-caliber machine guns.
The ships which served as high speed transports conducted some of the most back-breaking work of the war. They transported troops to beachheads, served as escorts for transports and supply vessels, conducted anti-submarine patrols and survey duties, operated with underwater demolition teams and commando units, performed messenger and transport duties, conveyed passengers and mail to and from forward units, and were involved in minesweeping operations. All the time they were subjected to attacks by aircraft, submarines, surface ships and kamikazes. Many of the ships suffered damage of some sort and a number were sunk during their operations.
