The Kingdom of Champasak declared itself independent from the Kingdom of Vientiane in 1713. The Kingdom of Champasak comprised the area south of the Xe Bang River as far as Stung Treng together with the areas of the lower Mun and Xi rivers on the Khorat Plateau (now the Isaan area of modern Thailand). The Kingdom was annexed by Siam in 1829 following the Chao Anouvong Rebellion, and subsequent kings were confirmed in Bangkok. From 1893 French took administrative control over parts of the kingdom, in 1904 the kingdom was reduced to a provincial governorship but still included the political involvement of the Na Champasak royal family. From 1941–45 Thailand exploited France's weakness during World War II to acquire Champasak and other Lao lands on the right bank of the Mekong. In 1946 Champasak was ceded back to France and Chao Boun Oum remitted all claims to an independent kingship in order to unify Laos. The Kingdom of Laos (1946–75) was then formed under the Luang Prabang line of kingship.