Scapa Flow - The defences of Britain's great fleet anchorage 1914-45

A strategically important natural harbor in the Orkney Islands, Scapa Flow served as Britain's main fleet anchorage during World Wars I and II. In 1914 and again in 1939, the British began building a comprehensive defensive network by fortifying the entrances to Scapa Flow, and then extended these defenses to cover most of Orkney.