The Probert Encyclopaedia of Ships

U-BOAT

U-Boats were German armed submarines used during the Great War and Second World War primarily to attack unarmed naval targets, such as merchant shipping. U-boats were of three types: coastal types; sea-going types and ocean-going types, differing primarily in size. The German U-boats of the Second World War were all single-hulled, unlike the earlier submarines used during the Great War which had a double-hull, and with a single-hull were more susceptible to damage from depth-charge attacks.
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