By 1974, half of Portugal's GDP and the vast majority of its armed forces were engaged in wars in three of Portugal's African colonies. Whereas other European powers had ceded independence to their former African colonies in the late 1950s and 1960s, Portuguese dictator António Salazar had refused to even countenance the option of independence. He had earlier resisted decolonization for the province of Goa, first occupied by the Portuguese in the 16th century, but was powerless to intervene when the Indian army marched in and incorporated the province into India in 1961. Salazar took the unusual step of appealing to the United Nations against the Indian action but was shunned (see Invasion of Goa). In 1968 Salazar's successor Marcelo Caetano continued the costly war in the colonies. By 1973, Portuguese control of Portuguese Guinea was collapsing rapidly. In Angola and Mozambique, it faced several guerrilla groups, like the Soviet-backed MPLA in Angola and FRELIMO in Mozambique. Losses in its conscript army, increasing military expenses, and the determination of the government to remain in control of the overseas territories disillusioned and radicalized the junior officers (the "captains") and even led right-of-center General António de Spínola to openly criticize the government's colonial policy. The junior officers formed the backbone of the military revolt against Caetano and the eventual overthrow of the Estado Novo regime.