The Kingdom of Thailand, covering an area of 514,000 square kilometers, lies in the heart of Southeast Asia, roughly equidistant between India and China. It shares borders with Myanmar to the west and north, Laos to the northeast, Kampuchea to the east and Malaysia to the south. Topographically the country is divided into four distinct areas: the mountainous North, the fertile Central Plains, the semi-arid plateau of the Northeast, and the peninsula South distinguished by its many beautiful tropical beaches and offshore Islands. A unified Thai kingdom was established in the mid-14th century; it was known as Siam until 1939. Thailand is the only southeast Asian country never to have been taken over by a European power. A bloodless revolution in 1932 led to a constitutional monarchy. In alliance with Japan during World War II, Thailand became a US ally following the conflict.