to surrender but the offer was not accepted. The city finally fell on 8 August 1569. Bayinnaung appointed Maha Thammaracha, the viceroy of Phitsanulok, as vassal king on 30 September 1569. The Burmese rule would not be challenged for another 15 years, until after Bayinnaung's death. Lan Xang (1569–1574) For Bayinnaung, the work was not yet done. On 15 October 1569, Bayinnaung at Ayutthaya led several regiments of his wounded army to invade Lan Xang via Phitsanulok. Setthathirath again fled Vientiane. Bayinnaung's men pursued but could not find him. Tired by long marches in a mountainous country, the Burmese army gave up and left Vientiane in May 1570. Another expedition in 1572 after Setthathirath's death also failed to bring order. Finally, the king himself led another expedition, and put his nominee on the Lan Xang throne in November 1574. Aside from a minor rebellion in 1579, Lan Xang gave no trouble for the rest of Bayinnaung's reign. Arakan (1580–1581) On 9 September 1580, Bayinnaung sent a large land and naval invasion force to bring Arakan, which was not yet part of his realm, the largest empire in the history of Southeast Asia. The combined forces (24,000 men, 1,200 horses, 120 elephants, 1,300 vessels) easily took Sandoway but did not proceed, awaiting the king's orders. The royal orders never came. The invasion forces withdrew in November 1581 after Bayinnaung's death. Collapse of Toungoo Empire Ava (1583–1584) Bayinnaung's massive empire began to unravel soon after his death. He had controlled his vast empire not only by exercising his massive military power but also by establishing personal connections with the vassal kings. The vassal kings were loyal to him as the universal ruler, Cakkavatti, not to the Kingdom of Toungoo. Bayinnaung's eldest son Nanda succeeded but faced an impossible task of keeping the ties together. The problems began close to home. Bayinnaung's three brothers, viceroys of Ava, Prome and Toungoo, only nominally acknowledged their nephew. In October 1583, Nanda discovered a plot by Thado Minsaw of Ava to overthrow him, and after an extensive preparation, marched to Ava in March 1584. On 24 April 1584, Nanda defeated Thado Minsaw in their elephant duel, and took Ava. Siam (1584–1593) Just nine days after the Ava rebellion was put down, on 3 May 1584, Siam also revolted. A few weeks earlier, the crown prince of Siam Naresuan's 6,000-strong army was hovering around Pegu instead of