Anawrahta
Lower Burma

After his first Shan campaign, Anawrahta turned to the Mon -speaking kingdoms in the south, which like Pagan were merely large city-states in reality. He first received submission of the ruler of Pegu (Bago). But the Thaton Kingdom refused to submit. Anawrahta's armies, led by the "Four Paladins", invaded the southern kingdom in early 1057. After a 3-months' siege of the city of Thaton, on 17 May 1057, (11th waxing of Nayon, 419 ME), the Pagan forces conquered the city.

According to Burmese and Mon traditions, Anawrahta's main reason for the invasion was Thaton king Manuha 's refusal to give him a copy of the Theravada Buddhist Canon. (Anawrahta had been converted to Theravada Buddhism from his native Ari Buddhism by Shin Arahan, a monk originally from Thaton.) In reality, it was merely a demand for submission couched in diplomatic language, and the real aim of his conquest of Thaton was to check the Khmer Empire 's conquests in the Chao Phraya basin and encroachment into the Tenasserim coast.

The conquest of Thaton is seen as the turning point in Burmese history. Still according to traditional reconstruction, Anawrahta brought back over 30,000 people, many of them artisans and craftsmen to Pagan. These captives formed a community that later helped build thousands of monuments at Pagan, the remains of which today rival the splendors of Angkor Wat.

More recent research by historian Michael Aung-Thwin has argued forcefully that Thaton's contributions to the cultural transformation of Upper Burma are a post-Pagan legend without contemporary evidence, that Lower Burma in fact lacked a substantial independent polity prior to Pagan's expansion, and that Mon influence on the interior is greatly exaggerated. Possibly in this period, the delta sedimentation—which now extends the coastline by three miles a century—remained insufficient, and the sea still reached too far inland, to support a population even as large as the modest population of the late precolonial era.

At any rate, during the 11th century, Pagan established its Lower Burma and this conquest facilitated growing cultural exchange, if not with local Mons, then with India and with Theravada stronghold Ceylon (Sri Lanka).
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