Thompson's first service at sea was on a merchantman, but he soon joined the
Royal Navy on in 1755, just before the outbreak of the
Seven Years' War. In the following five years he served on that ship then on
HMS Prince Frederick and (under Captain
Samuel Barrington) . He passed his examination for lieutenant in 1760 and was commissioned as the
fifth lieutenant of on 16 January 1761, serving on her in the
Channel Fleet and then in the
Mediterranean. When peace came, this ship was paid off and Thompson transferred to the sloop , serving on her on the
North American station from August 1763 to her paying-off in July 1768 in
South Carolina (with no transport provided to get her officers back to England, though they were later paid £39 0s. 6d each for the journey). Thompson was back in North America as 's
first lieutenant from May 1770, and there Commodore
James Gambier promoted him to
commander in February 1771, commanding the
sloop and then (after 3 months) appointed acting captain of . He took the later ship back to England in December 1771 and, though his acting captaincy was not confirmed by the admiralty, they did on 7 March 1772 promote him to full captain, commanding .
Service in the West Indies Thompson sailed to the
West Indies commanding , the
flagship of Vice-Admiral
William Parry, and later moved to the frigate . He returned to England in 1774, and then went back to the West Indies in command of in early 1776 (capturing the 20-gun French ship
Le Compas). He accompanied a merchant convoy to England in October 1777, before yet again going out to the West Indies in 1780. Sir
John Laforey was appointed commissioner of the shipyard at
Antigua in 1780, but Thompson refused to recognize this authority, leading to a long feud. In the Caribbean, Thompson was moved by Sir
George Rodney to the
74-gun , commanding her throughout the
American War of Independence, including at the battles of
the Chesapeake,
St Kitts, under
Sir Samuel Hood). In April 1782, Thompson was present in the rear division at the
Battle of the Saintes. Sir George Rodney's decisive victory over the French in the Caribbean. He sailed
Alcide back to England at the end of the War. == Later service ==