Near the end of the picture, as the ship is nearing Murmansk, several Russian airplanes fly out to meet it. One of the pilots keeps gunning his engine in short bursts. There are three short bursts followed by a long one. Movie audiences of the 1940s would immediately recognize this as the three dots and a dash of the Morse code "V". "V for Victory" was heavily used as a slogan during World War II.
Director Lloyd Bacon and producer Jerry Wald were prevented from filming at sea due to the US government's wartime restrictions, so the entire film was shot on Warner Bros.' sound stages and its back lot.
According to the book "Bill Collins Presents the Golden Years of Hollywood", "For certain scenes, amazingly created on the screen, a replica of a ten thousand-ton tanker was built inside Warner Brothers sound stages six and seven. Each stage contained one half the ship's hull and deck-housing fixtures. This ship had to be torpedoed with its gasoline cargo on fire [for the movie]. Then a Liberty Ship was constructed on the same two sound stages for later scenes in the film. Furthermore, the size of these sets prohibited their being fixed on gimbals. The rocking had to come from the camera, so the camera was mounted on a crane to simulate movement!"
While the convoy is ready to depart, naval flags for a number of countries are shown. One war-period flag is the Free French Naval Ensign, displaying the Cross of Lorraine, used from June 1940-May 1945.
Very few early World War II films featured African-Americans in the US military. Humphrey Bogart was quoted in "The Pittsburgh Courier" on 26 September 1942 as saying that he wanted to have a black Merchant Marine captain in this film. He said, "In the world of the theatre or any other phase of American life, the color of a man's skin should have nothing to do with his rights in a land built upon the self-evident fact that all men are created equal."