Good morning Walter,

The answers to your questions can be found in a book by Robert Gannon, "Hellions of the Deep, the development of American Torpedoes in World War II."

According to Gannon, there was some German knowledge of Fido but it was disregarded as something copied from "Popular Science" magazine by an unproductive spy. There was also a post war story about German aircrew rescue boat in the English Channel in the spring of 1943 finding a floating Mk 24 (Fido) recovering it and bringing it back to base. It was supposedly turned over to Luftwaffe scientists who determined it was an experimental unit with little potential and never bothered to tell the Kriegsmarine about their find.

Fido security was a very big deal because it would be easy to counter. According to Gannon some American scientists associated with the Fido program thought the Germans could develop a counter measure for it in less than a month if the had all the details on Fido.

Fido was replaced by the MK 34 torpedo which soldiered on into the 1960's until replaced by the MK 43's and MK 44's. The submarine adaptation of Fido technology was the MK 27 Torpedo or "cutie" used against the Japanese. It sank 24 ships and damaged 9. It also soldiered on into the 1960's in a Mod 4 configuration. As a submarine torpedoman I had two MK 27 Mod 4 warshots in the after torpedo room on USS Cusk SS-348 when we deployed to the Western Pacific for 6 months in 1962.