The crews of Portuguese Navy frigate NRP Afonso de Albuquerque and destroyer Dão mutinied against the Salazar dictatorship's support of General Franco's coup and declared their solidarity with the Spanish Republic.

The Portuguese Navy, also known as the Portuguese War Navy or as the Portuguese Armada, is the navy of the Portuguese Armed Forces. Chartered in 1317 by King Dinis of Portugal, it is the oldest continuously serving navy in the world; in 2017, the Portuguese Navy commemorated the 700th anniversary of its official creation.

NRP Afonso de Albuquerque was a warship of the Portuguese Navy, named after the 16th-century Portuguese navigator Afonso de Albuquerque. She was destroyed on 18 December 1961, defending Goa against the invading Indian Armed Forces Annexation of Goa.

NRP Dão was one of five Douro-class destroyer built for the Portuguese Navy during the 1930s. She remained in service until 1960, being refitted and re-armed several times and taking place in a coup attempt in 1936.

The 1936 Naval Revolt or Tagus boats mutiny was a mutiny in Portugal that occurred on 8 September 1936 aboard the aviso Afonso de Albuquerque and destroyer Dão. It was organized by the Revolutionary Organization of the Fleet, a left-wing group with links to the Portuguese Communist Party.

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.