The Kingdom of Laos was a sovereign state from 1953 until December 1975, when Communists overthrew the government and created the Lao People's Democratic Republic. Given self-rule in 1949 as part of a federation with the rest of French Indochina, the 1953 Franco-Lao Treaty finally established a sovereign, independent Laos, but did not stipulate who would rule the country. In the years that followed, three groups contended for power: the neutralists under Prince Souvanna Phouma, the right-wing party under Prince Boun Oum of Champassak, and the left-wing, Vietnamese-backed Lao Patriotic Front under Prince Souphanouvong and future Prime Minister Kaysone Phomvihane.