USS Dreadnaught (ID-1951), later YT-534 and YNG-21, was a United States Navy tug that was in service from 1918 to 1944. Construction, acquisition and commissioning Dreadnaught was built as a commercial tug of the same name by Union Iron Works at San Francisco, California, in 1917 for the Rolph Navigation and Coal Company of San Francisco. On 17 May 1917, the U.S. Navy purchased her for use during World War I and assigned her the naval registry identification number 1951. After fitting out at Mare Island Navy Yard at Vallejo, California, she was commissioned as USS Dreadnaught (ID-1951) on 31 January 1918. World War I service Departing San Francisco on 27 February 1918 towing coal barges, Dreadnaught delivered the barges at Norfolk, Virginia, on 18 April 1918. She then proceeded to New London, Connecticut, where she arrived on 22 April 1918. Dreadnaught was assigned to Patrol Force, United States Atlantic Fleet, and departed New London on 25 April 1918 to escort a convoy of submarine chasers to the Azores. On her return passage she aided in towing SS Luckenbach from the Azores to Bermuda and then towed the tug from Bermuda to New York City, arriving there on 1 July 1918. Between 6 September 1918 and 18 October 1918, Dreadnaught again escorted a group of submarine chasers from New London to the Azores and returned to New London. On 24 October 1918, she departed New London with a third convoy to the Azores, then proceeded to Brest, France, as escort for the United States Army tug Cuba. During the voyage, World War I ended, on 11 November 1918. The two tugs arrived at Brest on 29 November 1918. Dreadnaught should not be confused with the patrol vessel , which also was in commission during World War I. Postwar European and Atlantic service Dreadnaught operated on harbor duty at Brest and towed barges and ships between Brest, Lorient, and Bordeaux, France, until 20 March 1919, when she got underway to escort a convoy of submarine chasers to Lisbon, Portugal, and then on to Bermuda. She returned to Ponta Delgada in the Azores on 11 April 1919 for towing duty in the Azores until 29 July 1919. Towing submarine chasers, she returned to New York City on 19 August 1919. On 30 August 1919, she departed New York City for Norfolk, Virginia, with barges in tow, arriving at Norfolk on 1 September