A modern torpedo is an underwater ranged weapon launched above or below the water surface, self-propelled towards a target, and with an explosive warhead designed to detonate either on contact with or in proximity to the target. Historically, such a device was called an automotive, automobile, locomotive, or fish torpedo; colloquially a fish. The term torpedo originally applied to a variety of devices, most of which would today be called mines. From about , torpedo has been used strictly to designate a self-propelled underwater explosive device.
Modern torpedoes are classified variously as lightweight or heavyweight; straight-running, autonomous homers, and wire-guided types. They can be launched from a variety of platforms. In modern warfare, a submarine-launched torpedo is almost certain to hit its target; the best defense is a counterattack using another torpedo. Torpedo-like weapons were first proposed many centuries before they were successfully developed.
For example, in , engineer Hasan al-Rammah β who worked as a military scientist for the Mamluk Sultanate of Egypt β wrote that it might be possible to create a projectile resembling "an egg", which propelled itself through water, whilst carrying "fire".
In modern language, a "torpedo" is an underwater self-propelled explosive, but historically, the term also applied to primitive naval mines and spar torpedoes.
These were used on an ad hoc basis during the early modern period up to the late 19th century. In the early 17th century, the Dutchman Cornelius Drebbel , in the employ of King James I of England , invented the spar torpedo; he attached explosives to the end of a beam affixed to one of his submarines. These were used to little effect during the English expeditions to La Rochelle in In the early s, the American inventor Robert Fulton , while in France, "conceived the idea of destroying ships by introducing floating mines under their bottoms in submarine boats".
