Sea mine

Early 20th century

During World War I, mines were used extensively to defend coasts, coastal shipping, ports and naval bases around the globe. The Germans laid mines in shipping lanes to sink merchant and naval vessels serving Britain. The Allies targeted the German U-boats in the Strait of Dover and the Hebrides. In an attempt to seal up the northern exits of the North Sea, the Allies developed the North Sea Mine Barrage. During a period of five months from June 1918, almost 70,000 mines were laid spanning the North Sea's northern exits. The total number of mines laid in the North Sea, the British East Coast, Straits of Dover, and Heligoland Bight is estimated at 190,000 and the total number during the whole of WWI was 235,000 sea mines. Clearing the barrage after the war took 82 ships and five months, working around the clock. It was also during World War I, that the British hospital ship, HMHS Britannic, became the largest vessel ever sunk by a naval mine. The Britannic was the sister ship of the RMS Titanic, and the RMS Olympic.