At the outbreak of the war, Germany had only twenty submarines immediately available for combat, although these included vessels of the diesel-engined "U-19" class, which had a sufficient range of and speed of to allow them to operate effectively around the entire British coast., By contrast, the Royal Navy had a total of 74 submarines, though of mixed effectiveness. In August 1914, a flotilla of ten U-boats sailed from their base in Heligoland to attack Royal Navy warships in the North Sea in the first submarine war patrol in history.