On the 15th of March 1852 Lord Dalhousie sent an ultimatum to King Pagan, announcing that hostile operations would be commenced if all his demands were not agreed to by the ist of April. Meanwhile a force consisting of 8100 troops had been despatched to Rangoon under the command of General H.T. Godwin, C.B., while Commodore Lambert commanded the naval contingent. No reply being given to this letter, the first blow of the Second Burmese War was struck by the British on the 5th of April 1852, when Martaban was taken. Rangoon town was occupied on the 12th, and the Shwe Dagôn pagoda on the 14th, after heavy fighting, when the Burmese army retired northwards. Bassein was seized on the 19th of May, and Pegu was taken on the 3rd of June, after some sharp fighting round the Shwe-maw-daw pagoda. During the rainy season the approval of the East India Company's court of directors and of the British government was obtained to the annexation of the lower portion of the Irrawaddy Valley, including Prome. Lord Dalhousie visited Rangoon in July and August, and discussed the whole situation with the civil, military and naval authorities. In consequence General Godwin occupied Prome on the 9th of October after but slight resistance.
Early in December Lord Dalhousie informed King Pagan that the province of Pegu would henceforth form part of the British dominions, and that if his troops resisted the measure his whole kingdom would be destroyed. The proclamation of annexation was issued on the 20th of January 1853, and thus the Second Burmese War was brought to an end without any treaty being signed.
The imposition of an impossible fine on the Bombay-Burma Trading Company, coupled with the threat of confiscation of all their rights and property in case of non-payment, led to the British ultimatum of the 22nd of October 1885; and by the 9th of November a practical refusal of the terms having been received at Rangoon, the occupation of Mandalay and the dethronement of King Thibaw were determined upon. At this time, beyond the fact that the country was one of dense jungle, and therefore most unfavourable for military operations, little was known of the interior of Upper Burma; but British steamers had for years been running on the great river highway of the Irrawaddy, from Rangoon to Mandalay, and it was obvious that the quickest and most satisfactory method of carrying out the British campaign was an advance by water direct on the capital. Fortunately a large number of light-draught river steamers and barges (or "flats"), belonging to the Irrawaddy Flotilla Company, were available at Rangoon, and the local knowledge of the company's officers of the difficult river navigation was at the disposal of the government. Major-General, afterwards Sir, H.N.D. Prendergast, V.C., K.C.B., R.E., was placed in command of the expedition.
As was only to be expected in an enterprise of this description, the navy as well as the army was called in requisition; and as usual the services rendered by the seamen and guns were most important. The total effective of the force was 9034 fighting men, 2810 native followers and 67 guns, and for river service, 24 machine guns. The river fleet which conveyed the troops and stores was composed of a total of no less than 55 steamers, barges, launches, etc.
Thayetmyo was the British post on the river nearest to the frontier, and here, by 14th November, five days after Thibaw's answer had been received, practically the whole expedition was assembled. On the same day General Prendergast received instructions to commence operations. The Burmese king and his country were taken completely by surprise by the unexampled rapidity of the advance. There had been no time for them to collect and organize the stubborn resistance of which the river and its defences were capable. They had not even been able to block the river by sinking steamers, etc., across it, for, on the very day of the receipt of orders to advance, the armed steamers, the "Irrawaddy" and "Kathleen," engaged the nearest Burmese batteries, and brought out from under their guns the king's steamer and some barges which were lying in readiness for this very purpose. On the 16th the batteries themselves on both banks were taken by a land attack, the enemy being evidently unprepared and making no resistance.
On the 17th of November, however, at Minhla, on the right bank of the river, the Burmans in considerable force held successively a barricade, a pagoda and the redoubt of Minhla. The attack was pressed home by a brigade of native infantry on shore, covered by a bombardment from the river, and the enemy were defeated with a loss of 170 killed and 276 prisoners, besides many more drowned in the attempt to escape by the river. The advance was continued next day and the following days, the naval brigade and heavy artillery leading and silencing in succession the enemy's river defences at Nyaungu, Pakôkku and Myingyan. On the 26th of November, when the flotilla was approaching the ancient capital of Ava, envoys from King Thibaw met General Prendergast with offers of surrender; and on the 27th, when the ships were lying off that city and ready to commence hostilities, the order of the king to his troops to lay down their arms was received. There were three strong forts here, full at that moment with thousands of armed Burmans, and though a large number of these filed past and laid down their arms by the king's command, still many more were allowed to disperse with their weapons; and these, in the time that followed, broke up into dacoit or guerrilla bands, which became the scourge of the country and prolonged the war for years.
Meanwhile, however, the surrender of the king of Burma was complete; and on the 28th of November, in less than a fortnight from the declaration of war, Mandalay had fallen, and the king himself was a prisoner, while every strong fort and town on the river, and all the king's ordnance (1861 pieces), and thousands of rifles, muskets and arms had been taken. Much valuable and curious "loot" and property was found in the palace and city of Mandalay, which, when sold, realized about 9 lakhs of rupees (£60,000).
From Mandalay, General Prendergast seized Bhamo on the 28th of December. This was a very important move, as it forestalled the Chinese, who were preparing to claim the place. But unfortunately, although the king was dethroned and deported, and the capital and the whole of the river in the hands of the British, the bands of armed soldiery, unaccustomed to conditions other than those of anarchy, rapine and murder, took advantage of the impenetrable cover of their jungles to continue a desultory armed resistance. Reinforcements had to be poured into the country, and it was in this phase of the campaign, lasting several years, that the most difficult and most arduous work fell to the lot of the troops. It was in this jungle warfare that the losses from battle, sickness and privation steadily mounted up; and the troops, both British and native, proved once again their fortitude and courage.
Various expeditions followed one another in rapid succession, penetrating to the remotest corners of the land, and bringing peace and protection to the inhabitants, who, it must be mentioned, suffered at least as much from the dacoits as did the troops. The final, and now completely successful, pacification of the country, under the direction of Sir Frederick (afterwards Earl) Roberts, was only brought about by an extensive system of small protective posts scattered all over the country, and small lightly equipped columns moving out to disperse the enemy whenever a gathering came to a head, or a pretended prince or king appeared.
No account of the Third Burmese War would be complete without a reference to the first, and perhaps for this reason most notable, land advance into the enemy's country. This was carried out in November 1885 from Toungoo, the British frontier post in the east of the country, by a small column of all arms under Colonel W.P. Dicken, 3rd Madras Light Infantry, the first objective being Ningyan. The operations were completely successful, in spite of a good deal of scattered resistance, and the force afterwards moved forward to Yamethin and Hlaingdet. As inland operations developed, the want of mounted troops was badly felt, and several regiments of cavalry were brought over from India, while mounted infantry was raised locally. It was found that without these most useful arms it was generally impossible to follow up and punish the active enemy.