The Laotian Civil War (195375) was fought between the Communist Pathet Lao (including many North Vietnamese of Lao ancestry) and the Royal Lao Government in which both the political rightists and leftists received heavy external support for a proxy war from the global Cold War superpowers. Among United States Central Intelligence Agency Special Activities Division US and Hmong veterans of the conflict, it is known as the Secret War. The Kingdom of Laos was a covert theatre for battle for the other belligerents during the Vietnam War. The FrancoLao Treaty of Amity and Association signed 22 October 1953, transferred remaining French powers  except control of military affairs  to the Royal Lao Government  which did not include any representatives from the Lao Issara anti-colonial armed nationalist movement  and otherwise establishing Laos as an independent member of the French Union. The following years were marked by a rivalry between the neutralists under Prince Souvanna Phouma, the right wing under Prince Boun Oum of Champassak, and the left-wing Lao Patriotic Front under Prince Souphanouvong and future Prime Minister Kaysone Phomvihane. A number of attempts were made to establish coalition governments, and a 'tri-coalition' government was finally seated in Vientiane. The fighting in Laos involved the North Vietnamese Army, U.S., Thai, and South Vietnamese forces directly and through irregular proxies in a battle for control over the Laotian Panhandle. The North Vietnamese Army occupied the area for use as the Ho Chi Minh Trail supply corridor and staging area for offensives into South Vietnam. There was a second major theatre of action on and near the northern Plain of Jars. The North Vietnamese and Pathet Lao emerged victorious in 1975, as part of the general communist victory in Indochina that year.