Enemy civilians as prisoners of war

It might be a reasonable assumption that in times of war people from enemy countries should be rounded up and put in custody or detention. But there has to be a legal basis for this – it is a fundamental principle of English law that a subject cannot be held without just reason. 

At the outbreak of the First World War there were some 53,000 Germans and Austrians living in the country, with over half in London alone. Many of these were young men, economic migrants seeking employment opportunities. But these countries had a form of national service and such men had both undergone military training and were subject to recall to the army. And in the first days of the war many men did receive their call-up papers. 

The Geneva Conventions of 1906 and 1911 recognised such men as non-combatant enemy forces and gave them the right to be treated as prisoners of war. These de facto prisoners of war were then collected and sent to the great detention centres in the Isle of Man and Scotland.