peaceful for over 150 years, with a brief period of hostilities when King Narai of Ayutthaya launched an ill-fated expedition to vassalize Burmese-aligned Lan Na in the mid 17th century. The Konbaung dynasty had harbored to seize Ayutthaya's wealth and resources for the benefit of its own rulers. Siamese and Burmese interests in the Tenasserim have clashed on and off since the 16th century. Since the Burmese reconquest of Northern Tenasserim in the early 17th century, control of the economically lucreative Tenasserim coast was shared between Siam and Burma: Burma controlling the Northern Tenasserim ports of Mawlamyine and Tavoy while Siam controlled the Southern Tenasserim ports of Mergui and Tenasserim. Ayutthaya's support of the Mon rebels against Upper Burma, particularly in the aftermath of the fall of Lower Burma encouraged Alaungpaya to attempt an all-out attack on Ayutthaya in order to end Ayutthaya as a formidable opponent against Alaungpaya's interests for internal security and in an attempt to recreate Bayinnaung's conquests. Invasion of Ayutthaya After the rainy season of 1759, Alaungpaya and his armies returned to the south to deal with the still-unstable Lower Burma. One year back, a major Mon rebellion broke out, temporarily driving out the Konbaung governor of Pegu (Bago). Although the rebellion was put down, Mon resistance was still operating in the upper Tenasserim coast (present-day Mon State), where Konbaung control was still largely nominal. Siam provided shelter to the rebel leaders and their resistance troops. Alaungpaya sought assurances from the Siamese king that they would not intervene in the Burmese affairs and to surrender rebel leadership. But the Siamese king refused Burmese demands and prepared for war. In December 1759, Alaungpaya's 40,000-strong Burmese army left Martaban to invade Siam via Tenasserim. His second son, Hsinbyushin was his deputy. The Burmese occupied the town of Tenasserim, moved eastward over the Tenasserim Hills to the shore of the Gulf of Siam, turned north and captured the coastal towns, Kuwi, Pran Buri, and Phetchaburi. Siamese resistance stiffened as the Burmese approached the capital of Ayutthaya, but nonetheless, they were driven back with heavy losses in men, guns, and ammunition. The Burmese armies reached Ayutthaya in April 1760. Only five days into the siege, however, Alaungpaya suddenly fell ill. Thai sources say he was wounded by a cannon shell explosion while he was inspecting the cannon corps at the front, but Burmese sources state clearly that he fell ill,