[1] He was employed in a senior position in Admiral Thomas Graves's fleet owing to his extensive knowledge of the American coasts.

Douglas returned to England after the end of the war, initially spending time at Chatham Dockyard studying naval architecture, before going to sea again, mostly serving in the Mediterranean and the English Channel.

[7][8] The outbreak of the French Revolutionary Wars in February 1793 led to Douglas being appointed to command the 38-gun frigate HMS Phaeton.

[1][9] Lord Howe arranged for Douglas to be commodore in charge of the fleet's frigates, occasionally sending him on detached cruises.

[1] He moved aboard Howe's flagship, the 100-gun first rate HMS Queen Charlotte on 8 April 1794, apparently through the auspices of both his uncle and the First Lord of the Admiralty, John Pitt, 2nd Earl of Chatham.

Now serving as Howe's flag captain Douglas fought at the Glorious First of June, sustaining a severe wound to the head but refusing to leave the deck.

[1][11] He had begun to suffer increasing ill health, complaining of persistent headaches, which eventually forced him to end his career at sea.