In January 1776, for his "great vigilance and industry," Manley was appointed commodore of "George Washington's fleet", a group of small armed ships fitted out by him to harass the British and to seize supply vessels. The fleet was led by two frigates, and "Boston". On May 21, 1777 Manley's ships evaded the British blockade of the town of Boston and set sail for Newfoundland. A large British fleet was at anchor in nearby New York, but there was no pursuit as all British vessels were engaged in supporting troops stationed on shore. On June 7, Manley's ships encountered and defeated the 28-gun Royal Navy frigate in a brief engagement off the Grand Banks. Three weeks later they turned for the New England coast, in the hope of finding further British targets. By early July, Manley's fleet had made landfall off Nova Scotia. On July 7 they were discovered by a small force of two British frigates and a brig, who opened fire. After a running battle lasting 39 hours, the British succeeded in capturing both "Hancock" and "Boston", and retaking "Fox". Manley and his crew were imprisoned in New York until March 1778. Upon his release, Manley entered privateer service to command "Marlborough", "Cumberland", and a prize, "Jason", until 1782, except for two more periods of imprisonment, one for two years in Mill Prison, England. His privateer ship "Jason" was a small ship of 18 guns owned by Mungo Mackay and others. In November 1779, the ship fell in with the frigate Perseus and 18 were killed and 12 wounded on Jason, while 7 killed and several were wounded on the Perseus. On 11 September 1782, he returned to the Navy with command of frigate . On a West Indies voyage, he made a spectacular escape from a superior naval force and, in January 1783, took the last significant prize of the war, "Baille". Regarded as one of the outstanding captains of the young Navy, he had captured 10 prizes singlehandedly and participated in the seizure of five others. Captain Manley died in Boston, Massachusetts in 1793. Three ships have been named USS "Manley" for him.