The Mongol government could not ignore the situation any more. On 22 June 1300, the emperor declared Kumara Kassapa, a son of Kyawswa, the rightful king of Burma, and ordered an invasion. In the following dry season, a 12,000-strong Mongol army invaded, and despite taking heavy losses managed to reach Myinsaing on 25 January 1301. But Myinsaing's defences held, and the Mongols were persuaded to call off the attack on receipt of a considerable bribe on 6 April 1301. The Mongol government was dissatisfied with the outcome but pursued no further action. They withdrew from northern Burma entirely on 4 April 1303. Myinsaing was now the undisputed power in central dry zone of the country. At Pagan, Saw Hnit remained as "king" but in reality, he was now a mere governor. In the north, the brothers took over Tagaung but could not go any farther north as several Shan states now dominated the entire arc surrounding the Irrawaddy valley. In the south, they gained nominal allegiance of the rulers of Prome (Pyay) and Toungoo (Taungoo). They did not attempt to recover Lower Burma, which was now Ramanya, the coastal kingdom founded by the ethnic Mons. The triumvirate's rule lasted for a few more years in spite of Thihathu's ambitions. The youngest brother assumed a royal title in 1306, and proclaimed himself king on 20 October 1309. The proclamation ended the charade of Saw Hnit's nominal status as king. While it is not known what the two elder brothers made of the proclamation, after Athinkhaya's death in 1310, Thihathu emerged as the primary leader of central Burma. Yazathingyan faded into the background, and died two years later. The undisputed reign lasted about three years. In 1315, Thihathu's eldest biological son Saw Yun set up a rival base in Sagaing. By 1317, Saw Yun had survived two attacks by his father's forces, and the central dry zone was again divided: the Sagaing Kingdom in the north and the Pinya Kingdom in the south. The Myinsaing government was headed by the triumvirate. Although Myinsaing, Mekkhaya and Pinle were all capitals, judging by where they chose to defend against the Mongols, their hometown of Myinsaing appeared to have been the most important one. Like the Pagan government, the Myinsaing government relied on its vassal rulers for the governance of the peripheral regions.