Ships to transport troops were used in antiquity.
Ancient Rome used the
navis lusoria, a small vessel powered by rowers and sail, to move soldiers on the Rhine and Danube. The modern troopship has as long a history as
passenger 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 civilian
ocean 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 outrunning
submarines and enemy
cruisers in war. even rammed and sank a
U-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 in
convoys. 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 to
auxiliary cruisers during wartime. The British government, for example, aided both
Cunard and the
White Star Line in constructing the liners , , and
RMS Britannic. However, when the vulnerability of these ships to return fire was realized during
World War I most were used instead as troopships or
hospital ships. Soldiers were crowded onto troopships far exceeding normal capacity. carried 14,416 troops on one World War I trip, setting a record for the most humans on one vessel up to then. and were two of the most famous converted liners of
World 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. ==World War II==