Career
Spínola entered the Colégio Militar in 1920, beginning what would be a very successful military career. By 1928, Spínola was at Portugal's Military Academy, where he stood out as a young and promising cavalry officer.
In Anjos, Lisbon, by August 1932, he married Maria Helena Martin Monteiro de Barros (14 January 1913 – 23 May 2002), daughter of João de Azevedo Monteiro de Barros and his German wife Gertrud Elisabete Martin.
In 1939, he became adjunct-de-camp of the Guarda Nacional Republicana (Republican National Guard). In 1941 he travelled to the German-Russian Front, as an observer, to monitor Wehrmacht movements during the encirclement of Leningrad (the Portuguese volunteers had been incorporated into the Blue Division).
In 1961, guided by António de Oliveira Salazar, he offered himself for voluntary service in the Portuguese colonies of West Africa. Between 1961 and 1963, he held the command of the 345th Cavalry Battalion in Portuguese Angola, distinguishing himself and his unit. At the end of his tenure, he was appointed for, and served as, the Governor and Commander-in-Chief of the Armed Forces of the Portuguese Guinea from 1968, and again in 1972, during the period of the Overseas War, where his administration favoured a policy of respect for ethnic Guineans and the traditional authorities.
At the same time, he continued to practice a range of initiatives in the War. These included armed incursions to neighbouring states, most notably Operation Green Sea, which saw the assault by Portuguese Army Commandos into Conakry, Guinea. This operation was a failed attempt to carry out a coup against Ahmed Sékou Touré because of the latter's support for the independence movement PAIGC. Spínola also arranged clandestine meetings: in 1972 he met secretly with the president of Senegal, Léopold Sédar Senghor, to negotiate with the PAIGC, but he was rebuffed for this by Salazar's successor Marcelo Caetano.
In November 1973, he returned to Lisbon, on the invitation of Caetano, to head the Overseas portfolio. However, he refused this due to the government's intransigence on the Portuguese colonies. A month later, on 17 January 1974, he was asked to be the Vice-Chief of the Defence Council of the Armed Forces, on the advice of Francisco da Costa Gomes. Shortly later, he would publish Portugal e o Futuro (Portugal and the Future), which had at first been blocked from publication by the Portuguese censors. In this work, Spínola expressed the idea that the only solution to the Colonial Wars was the discontinuation of the conflict. He also defended a form of African "self-determination", yet without suggesting that the Portuguese colonies should gain independence, and suggested that Caetano should be replaced. The publication of the book swiftly led to Spínola's removal from the Defence Council.