Jeffords' mission is to knock out the submarine pens at Augusta, Sicily, because the Germans are storing radio-guided "glider bombs" there to be used against Allied shipping. While it sounds like a fantasy, the Germans did, in fact, have such weapons deployed in the Mediterranean theater in WW II - the world's first smart bombs. Nevertheless, the movie is set in 1942 and the first operational use of the Fritz X and Henschel 293 glide bombs did not occur until August 1943.
Filmed entirely on location in Malta including the 'Sicily' scenes.
A "hell boat" is World War II term used by the Germans for their motor torpedo E-boat.
The film's plot was based on the real life Second World War "Operation Ruthless" conceived by Ian Fleming.
American director (Paul Wendkos) was imported from Hollywood to helm this British World War II movie.