Fort Sullivan was a 19th-century military fortification in Eastport, Maine. It lay opposite New Brunswick, Canada, and served as an important coastal defense for the easternmost United States of America during the 19th century. As part of the establishment of New Ireland during the War of 1812, British Commodore Sir Thomas Hardy, 1st Baronet conquered the fort in 1814 and renamed it Fort Sherbrooke after John Coape Sherbrooke, the Governor of Nova Scotia.

Vice-Admiral Sir Thomas Masterman Hardy, 1st Baronet, GCB was a British Royal Navy officer. He took part in the Battle of Cape St. Vincent in February 1797, the Battle of the Nile in August 1798 and the Battle of Copenhagen in April 1801 during the French Revolutionary Wars. He served as flag captain to Admiral Lord Nelson, and commanded HMS Victory at the Battle of Trafalgar in October 1805 during the Napoleonic Wars. Nelson was shot as he paced the decks with Hardy, and as he lay dying, Nelson's famous remark of "Kiss me, Hardy" was directed at him. Hardy went on to become First Naval Lord in November 1830 and in that capacity refused to become a Member of Parliament and encouraged the introduction of steam warships.