A torpedo boat is a relatively small and fast naval ship designed to carry torpedoes into battle. The first designs rammed enemy ships with explosive spar torpedoes, and later designs launched self-propelled Whitehead torpedoes. They were created to counter battleships and other large, slow and heavily armed ships by speed and agility. A number of inexpensive boats attacking en masse could overwhelm a larger ship's ability to fight them off using its large, slow-firing guns. This way an inexpensive fleet of torpedo boats could defend against much larger and more expensive fleets, albeit only in the coastal areas to which their small size and limited fuel load restricted them.