without firing a shot. After the Battle of Naungyo, much of Lower Burma came under Toungoo rule by early 1539. Toungoo forces then sacked the last Hanthawaddy holdout, Martaban in May 1541, after a siege of seven months. After the mass execution at Martaban, southern territories (present-day Mon State) to the Siamese frontier submitted. The conquest of Martaban now gave the upstart regime of Tabinshwehti complete control of the maritime trade and ports of the Hanthawaddy Kingdom. More importantly, Toungoo now had access to Portuguese firearms, which would prove crucial in its future campaigns. Toungoo forces next attacked the Prome Kingdom, and drove back Prome's overlord Confederation and ally Arakan. After a five months' siege, Prome was mercilessly sacked in May 1542. In retaliation, the Confederation, consisted of seven Shan states, launched a major land and naval invasion in November 1543. But the invasion force was driven back, and was followed up by Toungoo forces which took as far north as the old imperial capital of Pagan. Tabinshwehti was crowned king at Pagan in July 1544. Ava did raid Salin in late 1544/early 1545 but the attack was easily repulsed. Arakan (1545–1547) Tabinshwehti then turned to Arakan, ally of Prome, invading the western kingdom by sea and land in October 1546. The combined forces quickly advanced to Mrauk-U but could not make any headway against the heavily fortified capital for the next three months. Hearing that the Siamese forces were raiding the frontier, Tabinshwehti agreed to a truce, and withdrew in February 1547. Siam (1547–1549) Back from Arakan, Tabinshwehti looked east to Siam, which had occupied what he considered his territory. His response to "Siamese incursions" would launch the centuries-long Burmese–Siamese Wars between Burma and Siam. Siamese sources deny that Siam began the hostilities; rather, it was Burma's attempt to expand its territory eastwards taking advantage of a political crisis in Ayutthaya that started the hostilities. (Either side's claim cannot be discounted since frontiers in the pre-modern period were less defined and often overlapped. The Tavoy frontier remained contested well into the 18th century.) The Burmese king sent a sizeable force (4000 naval, 8000 land troops) led by Gen. Saw Lagun Ein of Martaban to drive out the Siamese forces from Ye and Tavoy in late 1547. Saw Lagun Ein's forces defeated Siamese forces led by the governor of Kanchanaburi, and retook down to Tavoy. Tabinshwehti was not satisfied, and