Internment

Under the Fifth Hague Convention a neutral state had to intern belligerent troops that entered its territory, away from the theatre of war, in camps or fortresses; the costs were repaid after the peace. The Thirteenth Convention normally allowed warships to stay in a neutral port no longer than 24 hours, and a ship that did not leave was detained together with its crew. In this way thousands of soldiers from Antwerp were interned in the Netherlands in 1914, German auxiliary cruisers in the United States, and German troops from Cameroon in Spanish Guinea. From 1916 sick prisoners of war were interned in Switzerland.

The belligerents also interned enemy nationals, such as the British held at Ruhleben near Berlin, and people they suspected politically. After the oath crisis of 1917 the Germans interned Polish legionaries at Szczypiorno and Beniaminów. After the armistice the word took on a new meaning: the German High Seas Fleet was interned at Scapa Flow.