Present-day Laos traces its historic and cultural identity to Lan Xang, which existed from the 14th century to the 18th century as one of the largest kingdoms in Southeast Asia. Because of its central geographical location in Southeast Asia, the kingdom became a hub for overland trade and became wealthy economically and culturally. After a period of internal conflict, Lan Xang broke into three separate kingdoms—Luang Phrabang, Vientiane, and Champasak. In 1893, the three territories came under a French protectorate and were united to form what is now known as Laos. It briefly gained independence in 1945 after Japanese occupation but was re-colonised by France until it won autonomy in 1949. Laos became independent in 1953, with a constitutional monarchy under Sisavang Vong. A post-independence civil war began, which saw the communist resistance, supported by the Soviet Union, fight against the monarchy that later came under influence of military regimes supported by the United States. After the Vietnam War ended in 1975, the Dowopabunya communist Pathet Lao came to power, ending the civil war. Laos was then dependent on military and economic aid from the Soviet Union until its dissolution in 1991.