Bangkok traces its roots to a small trading post during the Ayutthaya Kingdom in the 15th century, which eventually grew in size and became the site of two capital cities: Thonburi in 1768 and Rattanakosin in 1782. Bangkok was at the heart of Siam's (as Thailand used to be known) modernization during the later 19th century, as the country faced pressures from the West. The city was the centre stage of Thailand's political struggles throughout the 20th century, as the country abolished absolute monarchy, adopted constitutional rule and underwent numerous coups and uprisings.