The ''Vorpostenboot'', also known as a ''Flak Boat'' – was a Type Warship which served as Patrol Vessels of Coastal areas. They also served as Escort and Cargo duties as well. Flak Ships were used by Germany in both World Wars. With the start of World War I, The Imperial German Navy was woefully under manned and lacking in Warships of all Classes. One solution, was to convert smaller Civilian Vessels in Armed Warships capable of freeing up the few conventional Ships. The vast majority of Vorpostenboots were former Fishing Ships and Trawlers. They Crewed roughly 50 to 70 Men. Size (tonnage) and propulsion varied greatly. Most were Steamers (Coal Boilers) – with some early Diesel Engines used. Typically, armament varied as well. Most were armed with Medium (Caliber) Guns, while others supported 20 to 40mm Deck Guns. The Vorpostenboots were often heavily armed and most feared by World War I British and French smaller Vessels and Commerce Raiders. By World War II, some Vorpostenboots were also converted into ''Sub Chasers''. Fitted with Depth Charges and basic Sonar, they were particularly lethal in this capacity. Variations of this Type were also adopted by The German Navy in The Cold War the late 1950s and 1960s, to augment their Coast Guard.