Tbh I think this is kind of misleading. Saying that "Burma has existed in one form or another for nearly 1500 years" comes with the corollary that the country has shattered into warring states multiple times since the 1200's.

Pagan Kingdom by late 1200's. Collapsed partially due to external foes (the Mongols).

"Small Kingdoms Period" for a nearly 300 year period (until 1555). Constituted of small, periodically warring states. Disintegration due to internal rebellions and external attackers was common.

One of the small states, the Taungoo Empire, managed to conquer the other states, and also surrounding territories. Taungoo nearly collapses once as Portuguese mercenaries attack, helping Arakan (aka the Rakhine state, home of the infamously oppressed Rohingya, and the subject of a recent attempted conquest by Taungoo). Taungoo recovers using more war to reclaim their conquests.

Rebellions from conquered groups occur, empire collapses for real this time. (1750's)

New dynasty from one of the break-up successor states, the Konbaung, reattack conquered areas in series of campaigns, including Rakhine State and others, etc, etc.

British Empire attacks, conquers region using gruesome tactics. Colonialism ensues.

Feel free to say that British colonial conquest and rule was terrible, because it was, but "Since its independence from the British you mean"? C'mon.