The chronic political instability and government's neglect of the army created opportunities for military plots. Already in 1925 there were two failed coup attempts on 18 April and 19 July. The plotters were acquitted by military court. During winter of 1925 and spring 1926 a group of junior officers planned a new coup and were looking for a senior officer to be the figurehead of their movement. They decided on General Manuel de Oliveira Gomes da Costa, who agreed to join the plotters on 25 May.
The revolution started in Braga, commanded by General Manuel Gomes da Costa, followed immediately in Porto, Lisbon, Évora, Coimbra and Santarém. The revolution triumphed when General Gomes da Costa marched on Lisbon along with 15,000 men, being acclaimed by the people of the city.
Timeline of events
General Manuel de Oliveira Gomes da Costa arrived at Braga with the purpose of initiating a coup d'état.
The First Portuguese Republic and Prime Minister António Maria da Silva, knowing of the forthcoming coup, tried to organize resistance -- believing an eventual coup d'état could be defeated.
A military coup d'état (hereinafter "the 28.5.26 coup d'état") began in Braga led by Gomes da Costa. Initially believing he failed, Gomes da Costa announced his surrender.
The 28.5.26 coup d'état spread to the rest of the country -- influenced Mendes Cabeçadas, Sinel de Cordes and Óscar Carmona -- and established the Ditadura Militar (National Military Dictatorship) against the democratic but unstable First Portuguese Republic.