Lan Xang
Laos traces its history to the kingdom of Lan Xang (Million Elephants), founded in the 14th century, by a Lao prince Fa Ngum, who with 10,000 Khmer troops, took over Vientiane. Ngum was descended from a long line of Lao kings, tracing back to Khoun Boulom. He made Theravada Buddhism the state religion and Lan Xang prospered. Within 20 years of its formation, the kingdom expanded eastward to Champa and along the Annamite mountains in Vietnam. His ministers, unable to tolerate his ruthlessness, forced him into exile to the present-day Thai province of Nan in 1373, where he died. Fa Ngum's eldest son, Oun Heuan, came to the throne under the name Samsenthai and reigned for 43 years. During his reign, Lan Xang became an important trade centre. After his death in 1421, Lan Xang collapsed into warring factions for the next 100 years.