In 1914, the young Portuguese Republic, two of whose first presidents came from the Azores, set itself the goal of resolving the national crisis that had arisen with the end of the monarchy. The intended stabilization was made more difficult by an unfavourable international environment. Six days after the outbreak of the First World War, the Congress of the Republic sided with Great Britain, but without simultaneously declaring itself against Germany. As a result, two opposing political currents brought society to the brink of civil war: those in favour of the war, who called for intervention on the side of Great Britain, faced those who were opposed to participation in the war.
The first group was close to the republican left, with leading figures being Afonso Costa, Norton de Matos and João Chagas. The opponents of the war were dominated by the republican and monarchist right, where Brito Camacho set the tone. In order to unite the factions, the pro-war supporters cited the threat to the Portuguese colonies as an argument. Further reasons for Portugal’s desire to enter the war were the attempt to consolidate the acceptance of the young republic within the international community and to strengthen the alliance with England at a time when there was a fear that the new state form and political sovereignty would be threatened by its Spanish neighbor.
In September 1914, the first Portuguese expeditionary force under the command of Lieutenant Colonel Alves Roçadas moved to Angola and Mozambique. Great Britain, interested in Portugal entering the war, subsequently put sustained pressure on the Portuguese government to confiscate the German warships and merchant ships docked in Portuguese ports that had sought refuge there after the war began. The seizure of German ships on February 23, 1916 led to the German Empire declaring war on the Republic of Portugal on March 9, 1916.
Starting in January 1917, a Portuguese expeditionary corps moved to Flanders. Inferior in terms of logistics and weapons technology, this corps lost almost half of its soldiers in the battle of La Lys during a brave resistance in the German spring offensive of 1918, with 1,300 killed, 4,600 wounded, 2,000 missing and over 7,000 prisoners.