In the early hours of 22 November 1970, six Portuguese warships surrounded Conakry, the capital of the Republic of Guinea, on the West African coast. Taking advantage of the darkness of the night, a military force landed on the northern and southern coasts of the sleeping city. At the head of these men was a young Portuguese marine officer, Commander Alpoim Calvao, who had been appointed to command this secret operation, codenamed Green Sea - Mar Verde in Portuguese. The main objective of the invasion was to promote a coup d'etat in the former French colony and overthrow the regime of President Sekou Toure, who supported the guerrillas of the PAIGC (African Party for the Independence of Guinea and Cape Verde), who were fighting for the independence of Portuguese Guinea. The invaders also sought to destroy the naval resources that the guerrillas and the Guinean navy had in the port of Conakry, capture the leader of the party, Amilcar Cabral, and rescue a group of Portuguese soldiers held in a PAIGC prison. The incursion would not have the expected success concerning the coup d'etat, and Portugal would be condemned by international organizations for the invasion of a sovereign state, but this operation would remain in the memory of many as the most daring carried out during the colonial war in Africa, although the Portuguese regime never recognised its involvement.

From 1963 to 1974, Portugal and its nationalist enemies fought an increasingly intense war for the independence of "Portuguese" Guinea, then a colony but now the Republic of Guinea-Bissau. For most of the conflict, Portugal enjoyed virtually unchallenged air supremacy, and increasingly based its strategy on this advantage. The Portuguese Air Force (Forca Aerea Portuguesa, abbreviated FAP) consequently played a crucial role in the Guinean war. Indeed, throughout the conflict, the FAP - despite the many challenges it faced - proved to be the most effective and responsive military argument against the PAIGC, which was fighting for Guinea's independence. The air war for Guinea is unique for historians and analysts for several reasons. It was the first conflict in which a non-state irregular force deployed defensive missiles against an organised air force. Moreover, the degree to which Portugal relied on its air power was such that its effective neutralisation doomed Lisbon's military strategy in the province. The FAP's unexpected combat losses initiated a cascade of effects that degraded in turn its own operational freedom and the effectiveness of the increasingly air-dependent surface forces, which felt that the war against the PAIGC was lost. The air war for Guinea thus represents a compelling illustration of the value - and vulnerabilities - of air power in a counter-insurgency context, as well as the negative impacts of overreliance on air supremacy.