Atroopship (alsotroop ship ortroop transport ortrooper) is aship used to carrysoldiers, either in peacetime or wartime. Troopships were often drafted from commercial shipping fleets, and were unable to land troops directly on shore, typically loading and unloading at aseaport or onto smaller vessels, eithertenders orbarges.

Attack transports,^[1] a variant of ocean-going troopship adapted to transporting invasion forces ashore, carry their own fleet of landing craft.Landing ships beach themselves and bring their troops directly ashore.

Ships to transport troops were used in antiquity.Ancient Rome used thenavis lusoria, a small vessel powered by rowers and sail, to move soldiers on the Rhine and Danube.^[2]

The modern troopship has as long a history aspassenger ships do, as most maritime nations enlisted their support in military operations (either by leasing the vessels or by impressing them into service) when their normal naval forces were deemed insufficient for the task. In the 19th century, navies frequently chartered civilianocean liners, and from the start of the 20th century painted them gray and added a degree of armament; their speed, originally intended to minimize passage time for civilian user, proved valuable for outrunningsubmarines and enemycruisers in war.HMT Olympic even rammed and sank aU-boat during one of its wartime crossings. Individual liners capable of exceptionally high speed transited without escorts; smaller or older liners with poorer performance were protected by operating inconvoys.

Most major naval powers in the late 19th and early 20th centuries provided their domestic shipping lines with subsidies to build fast ocean liners capable of conversions toauxiliary cruisers during wartime. The British government, for example, aided bothCunard and theWhite Star Line in constructing the linersRMS Mauretania,RMS Aquitania,RMS Olympic andRMSBritannic. However, when the vulnerability of these ships to return fire was realized duringWorld War I most were used instead as troopships orhospital ships.

Soldiers were crowded onto troopships far exceeding normal capacity.SS Leviathan carried 14,416 troops on one World War I trip, setting a record for the most humans on one vessel up to then.^[4]RMS Queen Mary andRMS Queen Elizabeth were two of the most famous converted liners ofWorld War II. When they were fully converted, each could carry well over 10,000 troops per trip.Queen Mary holds the all-time record, with 15,740 troops on a single passage in late July 1943, transporting 765,429 military personnel during the war.^[3]

Large numbers of troopships were employed during World War II, including 220 "Limited Capacity"Liberty ship conversions, 30Type C4 ship-basedGeneral G. O. Squier-class, a class of 84Victory ship conversions, and a small number of Type-C3-S-A2 ship-based dedicated transports, and 15 classes ofattack transports, of which some 400 alone were built.

• The modified Liberties were capable of transporting up to 450,^[6] 550,^[7] or 650^[8] (sources vary) troops orprisoners-of-war. Modifications included installation of bunks stacked five deep on the forwardtweendeck, additional shower andhead facilities, two additional diesel-powered generators,^[7] and installation of two more Oerlikon 20-mm automatic cannons.^{[6][7][9][10]}
• 30Type C4 ship-basedGeneral G. O. Squier-class, the largest carrying over 6,000 passengers.
• A class ofVictory ship-based dedicated troopship was developed late in World War II. A total of 84 such VC2-S-AP2 hull conversions was completed.^{[11][12][13][14][15]}
• A class ofType C3 ship – comprising mainly C3-S-A2 and C3-S-A3 hulls – was also converted to dedicated troopships, capable of carrying 2,100 troops,^[16] was also developed.
• At least 15 classes ofattack transport, consisting of at least 400 ships specially equipped for landing invasion forces rather than general troop movement.

The designation HMT (Her/His Majesty's Transport) would normally replace RMS (Royal Mail Ship), MV (Motor Vessel) or SS (Steamship) for ships converted to troopship duty with the United Kingdom's Royal Navy. The United States used two designations: WSA for troopships operated by theWar Shipping Administration usingMerchant Marine crews, and USS (United States Ship) for vessels accepted into and operated by the United States Navy. Initially, troopships adapted as attack transports were designated AP; starting in 1942 keel-up attack transports received the designation APA.

"HMT" was also used, for a while, to designate "Hired Military Transport."^[17]

In the era of theCold War, the United States designed theUnited States ship so that she could easily be converted from a liner to a troopship, in case of war. More recently,Queen Elizabeth 2 andCanberra were requisitioned by the Royal Navy to carry British soldiers to theFalklands War.^[18] By the end of the twentieth century, nearly all long-distance personnel transfer was done by airlift inmilitary transport aircraft.

• List of United States Navy amphibious warfare ships § Attack Transport (APA)
• List of United States Navy amphibious warfare ships § Amphibious Transport (LPA) - APA redesignation
• List of auxiliaries of the United States Navy § Transports (AP, T-AP)

• James Dugan,The Great Iron Ship, 1953 (regularly reprinted)ISBN 0-7509-3447-6
• Stephen Harding,Great Liners at War, Motorbooks Int'l, Osceola, WI, US, 1997ISBN 0-7603-0346-0
• Goron Newell,Ocean Liners of the 20th Century, Bonanza Books, US, 1963ISBN 0-517-03168-X

Media related toTroop ships at Wikimedia Commons

• British Armed Forces Website: Troopships

• Ship types
• Troop ships

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