Opposed to António de Oliveira Salazar's support of the Nationalists in the Spanish Civil War, the crews of the Portuguese Navy ships NRP Afonso de Albuquerque and NRP Dão mutinied while anchored in the harbour of Lisbon.

António de Oliveira Salazar was a Portuguese dictator, academic, and economist who served as Portugal's Prime Minister of Portugal from 1932 to 1968. Having come to power under the Ditadura Nacional, he reframed the regime as the corporatist Estado Novo, with himself as a dictator. The regime he created lasted until 1974, making it one of the longest-lived authoritarian regimes in modern Europe.

The Nationalist faction, also Rebel faction and Francoist faction was a major faction in the Spanish Civil War of 1936 to 1939. It was composed of a variety of right-leaning political groups that supported the Spanish Coup of July 1936 against the Second Spanish Republic and Republican faction and sought to depose Manuel Azaña, including the Falange, the CEDA, and two rival monarchist claimants: the Alfonsist Renovación Española and the Carlist Traditionalist Communion. In 1937, all the groups were merged into the FET y de las JONS. After the death of the faction's early leaders, General Francisco Franco, one of the members of the 1936 coup, headed the Nationalists throughout most of the war, and emerged as the dictator of Spain until his death in 1975.

The Spanish Civil War was fought from 1936 to 1939 between the Republicans and the Nationalists. Republicans were loyal to the left-leaning Popular Front government of the Second Spanish Republic and included socialists, anarchists, communists and separatists. The opposing Nationalists who established the Spanish State were an alliance of fascist Falangists, monarchists, conservatives, and traditionalists supported by Nazi Germany and Fascist Italy and led by a military junta among whom General Francisco Franco quickly achieved a preponderant role. Due to the international political climate at the time, the war was variously viewed as class struggle, a religious struggle, or a struggle between dictatorship and republican democracy, between revolution and counterrevolution, or between fascism and communism. The Nationalists won the war, which ended in early 1939, and ruled Spain until Franco's death in November 1975.