General Campbell, now a well-tried and war-worn veteran, might, like many of his brethren of the Peninsular campaigns, have fought over his Indian and European battles at a peaceful fireside at home, and "showed how fields were won" to the rising generation whom their country was about to summon into action. But the best and most important part of his military career was still to come, and in India, where he had first learned the profession of arms. Not long after his return to England, he joined the 38th regiment, of which he was appointed colonel, at the Cape, and proceeded with it to India, whither it had been ordered. On arriving in India, he was stationed at Berhampore, but was soon appointed by Sir E. Paget to take the command of the expedition fitted out against the Burmese. Of all the many nations of India, these people were reckoned among the bravest and most formidable; and their valour had already been shown in several severe repulses which they had given to the British troops, with whom they had but lately come in contact. The great aim of the expedition which General Campbell commanded was to take possession of Rangoon, the chief seaport of Burmah; and for this quarter he accordingly set sail, and anchored within the bar off the town on the 10th of May, 1823. The landing and capture of Rangoon were effected in twenty minutes with scarcely any resistance. A defensive war of stockades on the part of the Burmese followed, which they maintained with much spirit, and occasionally with success, until the close of the year, when they were emboldened to abandon their guerilla warfare, for which their country was highly favourable, for the precarious chances of a battle. They accordingly assembled a large army of between fifty and sixty thousand strong, with three hundred pieces of cannon, and came down upon the British, who did not exceed six thousand. This was what Campbell desired; the enemy were now before him in a fair field, instead of being intrenched behind stockades, or in the jungle, where they could not be reached except at great disadvantage. He saw at once that their wings were too far asunder, and he resolved to encounter them separately, and in quick succession. His plan was effectual; the enemy, thus attacked, were defeated in detail, and so completely, that they fled in wild disorder, leaving behind them their artillery, and throwing away their muskets. On the following day this crowd of fugitives was rallied, and incorporated with a new Burmese army that advanced to the scene of action; but Campbell attacked and defeated them in a second encounter that was as successful as the first. In these two engagements, the Burmese sustained a loss of more than five thousand men, while that of the British was only thirty killed and two hundred and thirty wounded. Undismayed, however, by such disasters, the enemy rallied for a third attempt, and this time were intrenched to the number of twenty thousand behind a strong stockade. Here they were attacked by General Campbell, and routed with such slaughter, that the war, for the time at least, was terminated by the submission of Burmah and the occupation of Rangoon. Few of our Indian campaigns were more glorious, if we take into account the obstacles which Campbell had to overcome, the smallness of his force as compared with that of the enemy, and the three decisive victories which he gained in such rapid succession. A full sense of his merit was manifested both in India and at home, by the thanks of the governor-general in council and the two houses of the British Parliament, while the Court of East India Directors voted him a gold medal and a pension of £1000 per annum for life, as the reward of his important services.

At the close of the Burmese war, General Campbell was appointed commander of the forces in the provinces on the coast of Tenasserim, which the enemy had ceded, and civil commissioner in the company’s affairs in relation to the kingdoms of Burmah and Siam. But the fatigues of the campaign had so permanently affected his health, that he was compelled to resign his command, and return to England in 1829. In the spring of 1831 he was appointed lieutenant-governor of New Brunswick, and in this province he continued nearly six years, and conducted the administration of its affairs not only to the satisfaction of the home government, but that of the colonists. In 1839 he was offered the appointment of commander-in-chief in Bombay, which he accepted, such an office being, of all others, the most congenial to his wishes; but almost immediately after, a fresh attack of ill health obliged him to resign it. After a few years of retirement from active life, which the increasing infirmities of old age rendered necessary, he died at Edinburgh, on the 6^th of October, 1843.