no limits on ships of under 600 tons. The French, Italian, Japanese and German Navies developed torpedo boats around that displacement, 70 to 100 m long, armed with two or three guns of around 100 mm (4 in) and torpedo launchers. For example, the Royal Norwegian Navy s were in fact of a torpedo boat size, while the Italian s were closer in size to a destroyer escort. After World War II they were eventually subsumed into the revived corvette classification. The Kriegsmarine torpedo boats were classified Torpedoboot with "T"-prefixed hull numbers. The classes designed in the mid-1930s, such as the Torpedo boat type 35, had few guns, relying almost entirely upon their torpedoes. This was found to be inadequate in combat, and the result was a "fleet torpedo boat" class (Flottentorpedoboot), which were significantly larger, up to 1,700 tons, comparable to small destroyers. This class of German boats could be highly effective, as in the action in which the British cruiser was sunk off Brittany by a torpedo salvo launched by the s T23 and T27. Motor torpedo craft Before World War I steam torpedo boats which were larger and more heavily armed than hitherto were being used. The new internal combustion engine generated much more power for a given weight and size than steam engines, and allowed the development of a new class of small and fast boats. These powerful engines could make use of planing hull designs and were capable of the much higher speed of under appropriate sea conditions than displacement hulls. The boat could carry two to four torpedoes fired from simple fixed launchers and several machine guns. During the First World War, three junior officers of the Harwich Force suggested that small motor boats carrying a torpedo might be capable of travelling over the protective minefields and attacking ships of the Imperial German Navy at anchor in their bases. In 1915, the Admiralty produced a Staff Requirement requesting designs for a Coastal Motor Boat for service in the North Sea. These boats were expected to have a high speed, making use of the lightweight and powerful petrol engines then available. The speed of the boat when fully loaded was to be at least and sufficient fuel was to be carried to give a considerable radius of action. They were to be armed in a variety of ways, with torpedoes, depth charges or for laying