Britain and her Allies persuaded neutral Portugal to impound 36 German ships moored off Lisbon, which they did on 24th February 1916. As a consequence of that action, Germany declared war on Portugal on 9th March 1916. Portugal are England’s oldest ally, dating back to the days of John O’Gaunt when the Anglo-Portuguese Alliance (or Aliança Luso-Britânica) was ratified at the Treaty of Windsor in 1386. Portugal sent men, equipment and medical personnel to help the Allies during WW1.
As with other countries of the world during the First World War, the women of Portugal, led by the wives of influential men, Army officers and members of the old aristocracy, mobilised and created or joined various organisations set up to help the soldiers and their wives and families, as well as orphaned children. One of those organisations was the Portuguese Women’s Crusade (CMP) founded on 20th March 1916 by Elzira Dantas Machado, wife of the President of the Republic. Their daughter, Maria Francisca Machado, trained as a nurse and went to the Western Front to care for sick and wounded Portuguese soldiers. Dr. Sofia da Conceicão Quintino was a Portuguese physician who organised the training of nurses.
Sources:
http://encyclopedia.1914-1918
online.net/article/womens_mobilization_for_war_portugal#GND_1060262290
With thanks
to Willy de Brouwer, Sabine Declercq and Mark Bristow via Facebook for additional information.