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 (now called the Pathet Lao) under Prince Souphanouvong and future Prime Minister Kaysone Phomvihane.
Many attempts were made to establish coalition governments: a Government of National Unity was established in 1958 under Prince Souvanna Phouma, but only survived a few months. The Prime Minister, who under the constitution appointed his ministers and received advice from the King, made a deal with his brother Prince Souphanouvong: Souvanna Phouma gave the Communists two seats in the Cabinet, and in return Souphanouvong would integrate 1,500 of his 6,000 Communist troops into the royal army. His half-brother was given the post of Minister of Planning, Reconstruction and Urbanization, while another member of the Communist Party was named Minister of Religion and Fine Arts.
The United States supplied the Royal Lao Navy with twenty river patrol boats and sixteen amphibious landing craft. Between 1962 and 1971, the United States provided Laos with an estimated US$500 million in military assistance, not including the cost of equipping and training irregular and paramilitary forces.
Alarmed by the growing power and influence of the Việt Minh, and fearing the spread of Communism, the United States began to provide aid "Indochina - United States Emergency Aid to Laos and Thailand in the Face of Viet Minh Aggression: Statement by the Secretary of State at a News Conference, May 9, 1953". "Yale Law School Avalon Project". "Lillian Goldman Law Library". Retrieved on 2008-07-19.. to Laos in 1953, in the process engendering widespread corruption within the Royal Lao Government. American involvement increased further in the early 1960s, when, in response to a perceived Soviet-backed Communist attempt to take over Laos, which was in direct violation of the 1963 Geneva agreement, the US launched a covert war in Laos. This involved a great deal of military support, including the training and equipping of RLG General Vang Pao’s forces in Xieng Khouang Province by US Special Forces, teams and the ferrying of men and equipment into Laos from Thailand by the CIA’s commercial airline, Air America.
A ceasefire was finally attained in February 1973, following the Paris Peace Accords between Washington, D.C. and Hanoi. In April 1974, another Provincial Government of National Unity was established, once more with Prince Souvanna Phouma as Prime Minister. However, by this time, Pathet Lao forces controlled large areas of the country, and following the fall of Saigon in April 1975 they advanced on the capital.
In December 1975 in Vientiane, Prince Vongsavang submitted the letter of abdication of King Savang Vatthana to the Pathet Lao. The Lao People's Democratic Republic was established with Prince Souphannavong as President. Kaysone Phomvihane acted as Prime Minister and Secretary-General of the Lao People's Revolutionary Party .