War Zones
those areas of the high seas which were officially designated as dangerous by the belligerent countries during the World War. Immediately after the outbreak of hostilities it became obvious that the Germans had strewn the waters of the North Sea with mines. In retaliation, and to prevent the escape of raiders from German ports, the British Admiralty announced in October, 1914, that it would have to follow "a mine-laying policy in certain areas."
A few months later these "areas" were made to include the whole of the North Sea, with the exception of certain lanes of safety, along which British war vessels guided friendly neutrals. In February, 1915, Germany proclaimed all the waters about the British Isles a war zone, with no safety lanes, announcing that all vessels entered this area at the risk of being sunk without warning. In January, 1917, Germany extended this zone down to include the French coasts in the Mediterranean, altogether including an area of over a million square miles.