The film is loosely based on the actual raid undertaken in 1942 by H.M.S. Campbeltown, in which the ship, loaded with explosives, rammed and subsequently destroyed the dock gates at the French port of Saint-Nazaire. This was the only dry dock outside of Germany able to accept and repair the German battleships Tirpitz and Bismarck. Just as in this story, the Campbeltown was formerly a US Navy destroyer, the USS Buchanan.
The ship portraying H.M.S. Ballentrae was actually H.M.S. Leamington. She was Lend Leased to the U.K. as one of the fifty Lend Lease destroyers in 1940. In an interesting twist, she was further loaned by the British to the Soviets in 1944, and named Zhguchi. She was returned in to the British in 1950 and scrapped in 1951. She was used for the set of this movie prior to scrapping.
Commander Fraser refers to his service medals as "Squeak" and "Wilfred". These were nicknames for the the British War Medal and the British Victory Medal of World War I. (Note: The 1914 Star and the 1914-15 Star star were nicknamed "Pip". The three names come from the names of characters in a Daily Mirror cartoon strip.)
This movie and "Attack on the Iron Coast" (1968) are based on the same World War II raid carried out by British forces on the locks of the French port of Saint-Nazaire in 1942.
The military mission in this movie is based on the real World War II raid on Saint-Nazaire by H.M.S. Campbeltown in an operation code named "Operation Chariot".