Angola was a colony of Portugal for more than 400 years from the 15th century. The demand for independence in Angola picked up momentum during the early 1950s. The Portuguese régime, refused to accede to the demands for independence, provoking an armed conflict that started in 1961 when freedom fighters attacked both white and black civilians in cross-border operations in northeastern Angola, which was called the Colonial War. The principal protagonists included the People's Movement for the Liberation of Angola (MPLA), founded in 1956, the National Front for the Liberation of Angola (FNLA), which appeared in 1961, and the National Union for the Total Independence of Angola (UNITA), founded in 1966. After many years of conflict that weakened all of the insurgent parties, Angola gained its independence on 11 November 1975, after the 1974 coup d'état in Lisbon, Portugal, which overthrew the Portuguese régime headed by Marcelo Caetano.