In the First World War, the so-called “Central Powers”, Germany, Austria-Hungary, and the “Triple
Entente”, France, Russia and Great Britain, faced each other. Portugal participated from 1916 onwards,
and the United States joined the “Triple Entente” as an ally in 1917.
The war was sparked by the assassination of the Austro-Hungarian Crown Prince in Sarajevo in June
1914, triggering a global conflict. The reason was the lack of capacity of the power blocs involved to
achieve political balance. This circumstance was based, in particular, on excessive nationalism and the
personal demands arising from it. There was also mutual distrust, which was further aggravated by an
arms race.
The conflict occurred in three phases. The first, which lasted only a few weeks, was characterized by a
rapid German offensive with large gains of territory in the west, while successfully repelling an attack by
Tsarist troops in the east. This war of movement quickly consolidated into a war of position in which
neither side was able to achieve decisive success. This phase lasted until the spring of 1918 and was
accompanied by unprecedented losses of fallen, wounded and missing soldiers.
In the maritime war during the second phase of the conflict, with the increase in German submarine
activity, the Azores became increasingly important as a possible safe haven and supply point on the
Atlantic route, as the US logistically supported Britain from the beginning, which was also the reason for
British efforts to persuade Portugal to enter the war.
After the entry of the United States into the war and the introduction of armored vehicles, the so-called
“tanks”, on the Allied side, the balance of economic and military power finally tipped in favor of the
Allies, which reflected in the German Spring of 1918, causing the Battle of La Lys, also directed against
the Portuguese army.
The final phase of the war ended on 11 November 1918 with the signing of an armistice, which was
followed by the conclusion of the Peace Treaty of Versailles on 28 June 1919.