in 1785, 1813 and 1849. Effective manpower control was one of major policies of the Siamese court in order to maintain stability and security. Population Surviving sources on the accurate population of pre-modern Siam does not exist. Only through the estimated projections that the demographic information of pre-modern Siam was revealed. In the first century of the Rattanakosin period, the population of what would become modern Thailand remained relatively static at around 4 million people. Fertility rate was high but life expectancy was averaged to be less than 40 years with infant mortality rate as high as 200 per 1,000 babies. Wars and diseases were major causes of deaths. Men were periodically drafted into warfare. Siamese children died from smallpox yearly and the Cholera epidemics of 1820 and 1849 had claimed 30,000 and 40,000 deaths, respectively. Bangkok was founded in 1782 as the royal seat and became the primate city of Siam. Bangkok inherited the founding population from Thonburi, which had already been enhanced by the influx of Lao and Cambodian war captives and Chinese and Mon immigrants. Through the early Rattanakosin period, the population of Bangkok was estimated to be around 50,000 people. Chinese immigration was the greatest contributor to the population of Bangkok and Central Siam. By the 1820s, Bangkok had surpassed all other cities in Siam in population size. Others estimated population of major town centres in Central Siam in 1827 included Ayutthaya at 41,350, Chanthaburi at 36,900, Saraburi at 14,320 and Phitsanulok at 5,000 people. Within the Siamese sphere of influence, Chiang Mai was the second most populated city in Rattanakosin Kingdom after Bangkok. Much of the western provinces of Siam were depopulated for several decades until the early 19th century due to the near-constant state of fighting with Burma. Succeeding Ayutthaya, the major Siamese city of Phitsanulok (another principal city of the former Ayutthaya Kingdom) was razed by the Burmese during the Burmese–Siamese War (1775–1776) in 1775. The Burmese–Siamese War (1809–1812), the last invasion into Siam by Burma, caused the depopulation of Phuket Island for several decades, and the destruction of Thalang, Phuket's then-main town, eventually to be overtaken by the new settlement of Phuket, as the island's resurgence as a tin mine settlement. Ethnic immigration Since the Thonburi period, Siam had acquired ethnic population through many campaigns against the neighbouring kingdoms. Ethnic war captives were forcibly relocated. In 1779, when the Siamese forces took