In June 1917 Portuguese troops saw their first action as battle-ready troops in France. Why is this significant? There is a tendency to highlight the entrance of the US in the First World War in 1917 but all of this shows the global nature of the war. It is true that Portugal had a long-standing agreement with the UK (and Great Britain, and England) and its entrance was part of this relationship but it was also about colonial possessions in Africa.
Prior to August 1914 the Germans and British had secretly been making plans to seize Angola and redistribute it but the onset of hostilities in Europe interrupted this plan. Instead, the two potential co-conspirators found themselves on opposite sides of the war, and the Portuguese did their best to interrupt trade for German Southwest Africa and even received assistance from the British to protect Mozambique from potential invasion. The African equilibrium had shifted.
Not surprisingly the Portuguese were happy with this shift and willingly acceded to British requests and in early 1916 interned both German and Austro-Hungarian ships that were in Portuguese ports at that point in time. Not surprisingly, the Germans considered this a belligerent act and declared war on Portugal in March 1916. One week later, Austria-Hungary followed suit. After deliberations in Parliament the Portuguese agreed to commit troops to the war effort. Given the needs on the Western Front, the Portuguese were charged with providing heavy artillery and its combat troops were integrated into the British Expeditionary Force.In response, perhaps, the Germans began U-Boat attacks on Portuguese islands: Madeira and the Azores were targeted; ships were sunk and seaside structures were targeted. There were several civilian fatalities in these assaults.
Compared to other countries, Portugal’s losses were modest: 8,145 soldiers died, another 13,750 were wounded and there were over 12,000 missing or prisoners of war. Ultimately, the former Habsburg Emperor Charles, lived his final days in Madeira, in relative obscurity but also comfort. Portugal acquired the Port of Kionga from the Germans – its only gain from its entrance in the war in a somewhat unwilling, unprovoked manner. And it was in the midst of a very turbulent time in Portuguese history, after the monarchy had been overthrown in 1910 but before the onset of a clear, right-wing dictatorship in 1926. It also deepened an economic crisis that had begun. And towards the end of the war, the situation was exacerbated by the onset of the Spanish Flu. Official statistics list 89000 dead as a result of war, but most of those were due to the flu.
Thus, the Great War had negative effects on the country: it may not have created a lost generation, or a serious diminution of the male population, but it further destabilized the country and contributed to the onset of civil war in 1926.