Army Transport Service

The United States Army Transport Service (ATS) operated Army transport ships for both troop transport and cargo service between United States ports and overseas posts. This service is often confused with the Army Transportation Service, created in France in 1917 to manage American Expeditionary Forces transport, renamed Transportation Corps 12 November 1918 still limited to France, becoming a general service under the Quartermaster Corps responsible for land and water transport, then briefly a name applied to a larger organization in the early days of World War II, and becoming the separate Transportation Corps effective 31 July 1942.

The Army Transport Service was established when the Army's difficulty in transporting its forces was exposed in the Spanish–American War with formal establishment in the fall of 1898 to operate under the Quartermaster Corps. ATS operated the Army's large ships but did not operate smaller vessels of the harbor boat service (tugs, launches, small and short range supply boats), the mine planters of the Coast Artillery Corps or any vessels of the Corps of Engineers. From that time until absorbed into the United States Army Transportation Corps to operate under its Water Division the service operated the United States Army Transports. Except during World War I, when the Army's large transports were turned over to the Naval Overseas Transportation Service (NOTS), ATS operated the sometimes sizable fleet of Army transports.

During peacetime ATS was to operate directly under the Quartermaster General through a General superintendent at home ports and in wartime, when formal ports of embarkation were to be established, ATS would come under the port commander's jurisdiction. During the interwar period ATS Atlantic was based at the New York General Depot, Army Supply Base, in Brooklyn and ATS Pacific and the transport docks were at the San Francisco General Depot, Fort Mason, California. The Army considered maintenance of a nucleus of military personnel, intimately familiar with both military requirements, port and ship operations, that could form the core of a full port of embarkation staff in wartime or other emergency as one of the reasons for maintaining ATS itself. Coordination with other Army transport functions was aided by the fact ATS was one of the four interwar divisions of the Army Transportation Service which also had divisions responsible for rail, motor and animal transport.

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