As Keppel, himself a hero, had been the first to discover kindred qualities in his young friend, so he was also the first who had the honour to reward the rising-genius of Mr Duncan. In January 1755, the commodore was selected to command the ships of war destined to convey the transports which had been equipped for the purpose of carrying out troops under general Braddock to North America, where the French had made various encroachments on British territory; and it was then that Keppel paid a compliment no less creditable to his own discrimination than flattering to Duncan's merits, by placing his name at the head of the list of those whom he had the privilege of recommending to promotion. Mr Duncan was accordingly raised to the rank of lieutenant; in which capacity he went on board the Norwich, captain Harrington. Soon after the arrival of the fleet in Virginia, the commodore removed Mr Duncan on board his own ship the Centurion, whereby he was placed not only more immediately under the friendly eye of his commander, but in a more certain channel of promotion. With the Centurion he returned to England, and remained unemployed (still the shipmate of Keppel, now on the home station) for three years. He was soon afterwards, however, called into active service, having been present at the attack on the French settlement of Goree on the coast of Africa; and the expectations which his commander had formed of him were amply realized by the bravery which he displayed in the attack on the fort. Before the return of the expedition he rose to the first lieutenancy of the commodore's ship, the Torbay.
In September, 1759, he was promoted to the rank of commander, and in February, 1761, being then in his thirtieth year, he obtained a post-captaincy. The ship to which on this occasion he was appointed was the Valiant, of seventy-four guns, on board which Keppel hoisted his flag, as commodore in command of the fleet which carried out the expedition to Belleisle. Here the critical duty of commanding the boats to cover the disembarkation of the troops devolved on captain Duncan, and in this, as in various other difficult and important services in which he was employed during the siege, he greatly distinguished himself. He had the honour, also, of taking possession of the Spanish ships when the town surrendered to the English.
In the year following, he sailed with the Valiant in the expedition under admiral Pocock, which reduced the Havannah; and he remained in command of the same vessel till the conclusion of the war, in 1763. The powers of Europe, notwithstanding the exhausting conflicts in which they had for many years been engaged, were still too heated to remain long at peace, and the war which followed, again called into active operations all the energies of the British navy. No opportunity, however, occurred that enabled Duncan, now commander of the Suffolk of 74 guns, to distinguish himself. On returning to England on the temporary cessation of hostilities, he had the singular fortune of being called to sit as a member of the court-martial which was held on his brave and injured friend, admiral Keppel, whose unanimous and most honourable acquittal was immediately followed by votes of thanks from both houses of parliament for his distinguished services. He discharged perhaps a less irksome, but a not less impartial duty, on the trial of Keppel's accuser, Sir Hugh Palliser, who, suffering under the censure of the court, and the resentment of the nation, was forced to relinquish all his public offices.
In the summer of 1779, captain Duncan commanded the Monarch, 74, attached to the channel fleet under Sir Charles Hardy; and towards the conclusion of the year, he was placed under the orders of Sir George Rodney, who sailed with a powerful squadron to attempt the relief of Gibraltar. This armament, besides effecting the purpose for which it had been sent out, had the good
