The Lao kingdom of Lan Chang was established in 1354 by Fa Ngum.
Exiled as an infant to Cambodia, Prince Fa Ngum of Xieng Dong Xieng Thong married a daughter of the Khmer king. In 1349 he set out from Angkor at the head of a 10,000-man army to establish his own country. Fa Ngum organized conquered principalities into provinces (muang), claimed the crown of Xieng Dong Xieng Thong from his father and elder brother and in June 1354 was crowned ruler of Lan Xang at Vientiane, the site of one of his victory of Phay Nam. The "million elephants" of the kingdom's name alluded to his formidable war machine. The Kingdom of Lan Xang extended from the borders of China south to Sambor below the Mekong rapids at Khong Island, and from the Vietnamese border to the western escarpment of the Khorat Plateau. It was thus one of the largest kingdoms in Southeast Asia.
The early years of Fa Ngum's rule were uneventful. However, the next six years (1362 to 1368) were troubled by conflict between Fa Ngum's Mahayana Buddhism and the region's traditional Theravada Buddhism. He severely repressed popular agitation and had many temples torn down. In 1368 Fa Ngum's Khmer wife died. He then married a daughter of the king of Ayutthaya, who seems to have had a pacifying influence on her husband. She was instrumental in welcoming a religious and artistic mission that brought a carved figure of the Buddha, the Phra Bang, for which the capital was renamed Luang Prabang. Popular resentment continued to build, however, and in 1373 Fa Ngum withdrew to Muang Nan. His son, Oun Heuan, who had been in exile in southern Yunnan, returned and assumed the regency of the kingdom his father had created. Oun Heuan succeeded Fa Ngum on his death in 1393, calling himself King Samsenethai (300,000 Thais), ending Mongol overlordship of the middle Mekong Valley.
The kingdom of Lan Xang, made up of Laos, Thais, and various ethnic hill tribes, lasted for another 300 years and briefly reached an even greater extent in the northwest. Fa Ngum's descendants remained on the throne for almost 600 years after his death. They maintained the independence of Lan Xang to the end of the 17th century by a complex network of vassal relations with lesser princes. At the same time, the rulers fought off invasions from Vietnam (1478-79), Siam (1536), and Burma (1571-1621).
In 1694, a series of rival pretenders to fought for the throne throne, and in 1707 the country split into three kingdoms: Luang Prabang, Vientiane, and Champasak, each of which paid tribute to Ayutthaya. Muang Phuan enjoyed a semi-independent status as a result of having been annexed by a Vietnamese army in the 15th century, an action that set a precedent for a tributary relationship with the court of Viet Nam at Hué.
