[1] Portugal was taking part in World War I, a participation that was largely unpopular due to its social and economic impacts,[1][2][3] and that the government tried to contain using repressive measures.

[1] A conspiracy emerges within the Unionists, initially supported by its leader Manuel de Brito Camacho, but who later had a change of heart and did not participate in the coup.

[2] On the night of 5 December 1917, Sidónio Pais, with the support of multiple units of the Army, occupied the Eduardo VII Park and the main roads of access.

[1] The Navy, positioned in the Tagus river and led by Leote de Rego aboard the destroyer Guadiana, exchange fire with the rebel forces in Eduardo VII.

[1] Another column attempts to attack from Rato, supported by artillery placed in the São Pedro de Alcântara garden (in Bairro Alto).