Although small by naval standards, it was larger than the preceding Coastal Motor Boats of 40 and 55 ft length. The first motor launches entered service in the First World War. These were 580 80-foot-long (24 m) vessels built by the US Elco company for the Admiralty, receiving the designations ML-1 to ML-580. They served between 1916 and the end of the war with the Royal Navy defending the British coast from German submarines. Some of the earliest examples, including ML 1, also served in the Persian Gulf from June 1916 onwards. After the Armistice of 11 November 1918 a flotilla of 12 RN Motor Launches traveled down the Rhine performing duty as the Rhine Patrol Flotilla.