The Mark 24 torpedo, nicknamed “Fido” for its ability to sniff out enemy submarines, was one of the first “smart” weapons developed during World War II. An official definition for smart weapons does not exist, but such devices are characterized by a set of sensors—electromagnetic, acoustic, heat, etc.—that enable the weapon to precisely home in on its target. Those smart weapons that are not directed from the launch platform via a wire, radio control, laser illumination, or radar signals are said to be autonomous, or fire-and-forget weapons; once launched the platform is free to take evasive action or continue its mission. The Fido fell into this category.
The idea for an acoustically directed torpedo originated in Division 6 of the National Defense Research Committee (NDRC) established by President Franklin D. Roosevelt in June 1940 to coordinate, supervise, and conduct scientific research on the problems underlying the development, production, and use of mechanisms and devices of warfare.