lines, dated 1755, is in the British Museum. On 1 Sept. 1756 he received a commission as lieutenant in the 37th foot, then serving in Germany, and in the following year returned to survey work in Scotland. On 14 May 1757 he became a lieutenant of royal engineers.
Debbieg was promoted to be captain-lieutenant on 4 Jan. 1758, and shortly after proceeded on active service to North America. He arrived at Halifax, Nova Scotia, on 9 May, and joined the expedition under Major-general Jeffrey (afterwards Lord) Amherst [q. v.] against Louisbourg. He took part in the action on landing at Cape Breton on 8 June, and was assistant quartermaster-general under Wolfe at the siege of Louisbourg from 11 June until its capitulation on 26 July. The siege was a difficult one, and Debbieg, who was a man after Wolfe's own heart, resolute and daring, giving little heed to rule or system where they interfered with his views of the best mode of attack, had many opportunities of displaying his valuable qualities. He was promoted to be captain on 17 March 1759.
He served under Wolfe as assistant quartermaster-general throughout the campaign of 1759 in Canada, was present at the siege of Quebec frum 10 July to 18 Sept., at the repulse of Montmorency on 31 July, at the battle on the plains of Abraham on 13 Sept., and in the operations which terminated with the capitulation of the garrison at Quebec on 18 Sept. During the actual siege he temporarily gave up his appointment on Wolfe's staff to take his share of the engineer duties. He was with Wolfe when he fell, and figures in West's celebrated painting of the incident.
Debbieg was at the battle of Sillery on 28 April 1760, and served in the stubborn defence of Quebec against the French until the siege was raised on 17 May. Subsequently he took part in the operations to complete the subjugation of Canada, ending with the capitulation of Montreal on 8 Sept. He accompanied the army to Halifax, Nova Scotia, where he acted for a time as chief engineer during the absence of Colonel Bastide.
In 1762, the French having seized Newfoundland, Debbieg accompanied the expedition sent to recapture it, landing with the troops at Torbay, nine miles from St. John's, under a heavy fire on 12 Sept. On the same day he took part in the action of Quiddy-Viddy and the attack on St. John's, which surrendered on the 18th, and with it the whole of Newfoundland. Debbieg sent home a plan of the operations of the troops, showing the town, harbour, and vicinity of St. John's. He repaired the defences and designed new works to replace some which had become obsolete. In 1763 he extended his surveys to Grace and Carboniere harbour in Conception Bay. In the following year he returned to England.
In 1765 he was appointed chief engineer in Newfoundland, but did not proceed thither until June 1766. In 1767 he was sent on a secret mission to France and Spain. He made plans of Barcelona, Carthagena, Cadiz, and Coruna, which are in the British Museum, together with a manuscript entitled 'Remarks and Observations on several Seaports in Spain and France during a Journey in those Countries in 1767-1768.' During these travels he was subjected to suspicion, ill-treatment, and confinement, for he was not at liberty to divulge his profession or the purpose of his travels. His mission was, however, successfully accomplished, and for his efficiency, ardour, and tact George III granted him a pension for life of 1l. per diem on 10 March 1769.
In this year he served on the committee of engineers at Westminster to report on the works necessary to complete the defences of Gibraltar. In the meantime his proposals for the defence of Newfoundland had been in abeyance on account of the cost, and at the end of 1770, having, much against his will, submitted an inferior but less costly scheme of defence, it was ordered to be carried out. On 23 July 1772 he was promoted to be brevet major, and during the next three years was employed in various secret missions, which he carried out to the satisfaction of the government.
In December 1775 he was appointed chief engineer in America on the application of Sir Guy Carleton (afterwards first baron Dorchester) [q. v.] for his services for the defence of Quebec, but for reasons not now traceable he resigned the appointment. On 29 Aug. 1777 he was promoted to be brevet lieutenant-colonel, and in the autumn was selected as chief engineer on the staff of Jeffrey, Lord Amherst, commander-in-chief. On 17 March 1778, in addition to his staff duties, he was appointed chief engineer at Chatham. He carried out the approved designs by Desmaretz and Skinner for the defence of Chatham, but criticised them unfavourably. He constructed a military bridge across the Thames between Tilbury and Gravesend, formed of barges so arranged that a cut could be easily made for navigation. This bridge was maintained until the invasion scare had passed away. In 1779 his proposed additions to the defences of