In 1783 the new king effected the conquest of Arakan. In the same year he removed his residence from Ava, which, with brief interruptions, had been the capital for four centuries, to the new city of Amarapura, "the City of the Immortals."

The Siamese who had revolted in 1771 were never afterwards subdued by the Burmans; but the latter retained their dominion over the sea-coast as far as Mergui. In the year 1785 they attacked the island of Junkseylon with a fleet of boats and an army, but were ultimately driven back with loss; and a second attempt by the Burman monarch, who in 1786 invaded Siam with an army of 30,000 men, was attended with no better success. In 1793 peace was concluded between these two powers, the Siamese yielding to the Burmans the entire possession of the coast of Tenasserim on the Indian Ocean, and the two important seaports of Mergui and Tavoy.

In 1795 the Burmese were involved in a dispute with the British in India, in consequence of their troops, to the amount of 5000 men, entering the district of Chittagong in pursuit of three robbers who had fled from justice across the frontier. Explanations being made and terms of accommodation offered by General Erskine, the commanding officer, the Burmese commander retired from the British territories, when the fugitives were restored, and all differences for the time amicably arranged.

But it was evident that the gradual extension of the British and Burmese territories would in time bring the two powers into close contact along a more extended line of frontier, and in all probability lead to a war between them. It happened, accordingly, that the Burmese, carrying their arms into Assam and Manipur, penetrated to the British border near Sylhet, on the north-east frontier of Bengal, beyond which were the possessions of the chiefs of Cachar, under the protection of the British government. The Burmese leaders, arrested in their career of conquest, were impatient to measure their strength with their new neighbours. It appears from the evidence of Europeans who resided in Ava, that they were entirely unacquainted with the discipline and resources of the Europeans. They imagined that, like other nations, they would fall before their superior tactics and valour; and their cupidity was inflamed by the prospect of marching to Calcutta and plundering the country. At length their chiefs ventured on the open violation of the British territories. They attacked a party of sepoys within the frontier, and seized and carried off British subjects, while at all points their troops, moving in large bodies, assumed the most menacing positions.

In the south encroachments were made upon the British frontier of Chittagong. The island of Shahpura, at the mouth of the Naaf river, had been occupied by a small guard of British troops. These were attacked on the 23rd of September 1823 by the Burmese, and driven from their post with the loss of several lives; and to the repeated demands of the British for redress no answer was returned. Other outrages ensued; and at length, on March 5th, 1824, war was declared by the British government. The military operations, which will be found described under Burmese Wars, ended in the treaty of Yandaboo on the 24th of February 1826, which conceded the British terms and enabled their army to be withdrawn.

For some years the relations of peace continued undisturbed. Probably the feeling of amity on the part of the Burmese government was not very strong; but so long as the prince by whom the treaty was concluded continued in power, no attempt was made to depart from its main stipulations. That monarch, Ba-ggi-daw, however, was obliged in 1837 to yield the throne to a usurper who appeared in the person of his brother, Tharrawaddi (Tharawadi). The latter, at an early period, manifested not only that hatred of British connexion which was almost universal at the Burmese court, but also the extremest contempt. For several years it had become apparent that the period was approaching when war between the British and the Burmese governments would again become inevitable. The British resident, Major Burney, who had been appointed in 1830, finding his presence at Ava agreeable neither to the king nor to himself, removed in 1837 to Rangoon, and shortly afterwards retired from the country. Ultimately it became necessary to forego even the pretence of maintaining relations of friendship, and the British functionary at that time, Captain Macleod, was withdrawn in 1840 altogether from a country where his continuance would have been but a mockery.

The state of sullen dislike which followed was after a while succeeded by more active evidences of hostility. Acts of violence were committed on British ships and British seamen. Remonstrance was consequently made by the British government, and its envoys were supported by a small naval force. The officers on whom devolved the duty of representing the wrongs of their fellow-countrymen and demanding redress, proceeded to Rangoon, the governor of which place had been a chief actor in the outrages complained of; but so far were they from meeting with any signs of regret, that they were treated with indignity and contempt, and compelled to retire without accomplishing anything beyond blockading the ports. A series of negotiations followed; nothing was demanded of the Burmese beyond a very moderate compensation for the injuries inflicted on the masters of two British vessels, an apology for the insults offered by the governor of Rangoon to the representatives of the British government, and the re-establishment of at least the appearance of friendly relations by the reception of a British agent by the Burmese government.

But the obduracy of King Pagan, who had succeeded his father in 1846, led to the refusal alike of atonement for past wrongs, of any expression of regret for the display of gratuitous insolence, and of any indication of a desire to maintain friendship for the future. Another Burmese war was the result, the first shot being fired in January 1852. As in the former, though success was varying, the British finally triumphed, and the chief towns in the lower part of the Burmese kingdom fell to them in succession. The city of Pegu, the capital of that portion which, after having been captured, had again passed into the hands of the enemy, was recaptured and retained, and the whole province of Pegu was, by proclamation of the governor-general, Lord Dalhousie, declared to be annexed to the British dominions on the 20th of December 1852. No treaty was obtained or insisted upon, - the British government being content with the tacit acquiescence of the king of Burma without such documents; but its resolution was declared, that any active demonstration of hostility by him would be followed by retribution.