Director Lloyd Bacon's contract with Warner Bros. expired during production. Jack L. Warner told him, "Finish the picture and we'll talk about it," but Bacon wasn't willing to continue without a contract. Warner fired him and brought in Byron Haskin to finish the film.
When shooting the scene early in the movie, when their characters abandoned ship from their burning tanker, Humphrey Bogart and Raymond Massey got into a friendly argument over who had the better stunt double. In the end, the two stars decided to do away with their stunt doubles altogether and wound up doing the stunt themselves. Massey elaborates on this anecdote in detail in his autobiography, 'A Hundred Different Lives'.
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" by Bill Collins, "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 rocking equipment. The rocking had to come from the camera, so the camera was mounted on a crane to simulate movement!".
Near the end of the picture, as the ship is nearing Murmansk, several Russian airplanes fly out to meet them. 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.
According to the book "The Films of World War II' by Joe Morella, Edward Z. Epstein and John Griggs, at the film's premiere in New York on May 21, 1943, Warner Brothers studio chief Jack L. Warner was presented with the Merchant Marine's Victory Flag by 300 sailors, 17 torpedo seamen and the US Merchant Marine band. The seamen first marched into the auditorium before the presentation. Apparently, this was "the first war pennant awarded to a member of the film industry."
This movie's opening prologue is a quote from Franklin D. Roosevelt. It reads: "Today in the face of this newest and greatest challenge of them all, we of the United Nations have cleared our decks and taken our battle stations. It is the will of the people that America shall deliver the goods. It can never be doubted that the goods WILL be delivered by this nation, which believes in the tradition of 'DAMN THE TORPEDOES; FULL SPEED AHEAD!'" 'Franklin D. Roosevelt'
This movie's marketing connected the film with two of the studio's earlier pictures, Sergeant York (1941) and Air Force (1943), by saying that the picture was "in the heroic tradition" of these two earlier movies.
Alvah Bessie, a writer who worked uncredited on this film, once wrote, according to Bill Collins in his book "Bill Collins Presents the Golden Years of Hollywood", that this movie " . . . was one of very few movies made in America which not only showed there was a trade union movement, but also had scenes in the union hall, said a few basic things about unionism and showed what being a union member could mean for a man."
Several writers who worked on the picture, including John Howard Lawson, A.I. Bezzerides and an uncredited Alvah Bessie, were later investigated by the House Un-American Activities Committee for "subversive" activities and blacklisted. Bessie and Lawson became known as as members of the Hollywood Ten, a group of writers and directors who refused to answer questions from the Committee by invoking their Fifth Amendment rights under the US Constitution and who were subsequently sent to prison for doing so.
Reportedly Warner Bros. had originally intended to make only a two-reel documentary on the Merchant Marines, but as the war progressed, it was decided to make an entire feature film instead, the result of which was this film.
Julie Bishop and Raymond Massey repeated their roles of Pearl O'Neill and Captain Steve Jarvis on radio in a "Lux Radio Theatre" broadcast on May 15, 1944. The program also starred George Raft, who was originally to appear in the film before production began.
Very few early World War II films featured African-Americans in the US military. Star 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."
At the end of the movie, Humphrey Bogart says, "I'm just thinking about the trip back." This is a double entendre. On the one hand it means the voyage back home may encounter rough seas and/or weather, but there is also an interpretation relating to Russians seen rejoicing at the end of this picture. Bogart does not return their friendly advances and remains quiet and a seaman asks why. The "I'm just thinking about the trip back" line can be considered a reference to having to deal with the Russian comrades, something which is ironic considering the film does have pro-unionist and left-wing political dialogue elements in the script. This line was cut out of the movie often when it played on television in America.
According to A.I. Bezzerides in the book "Screenwriter: Words Become Pictures", some of the scenes written by writer John Howard Lawson were "so out of context in their propagandistic way that the actors couldn't act them." Bezzerides cited scenes involving Humphrey Bogart and Julie Bishop and Raymond Massey and Ruth Gordon in particular. He went on to say that he polished every scene in the film and deserved credit, but Lawson fought against it. Bezzerides claimed that Lawson had so many friends in the Writers Guild that he lost the arbitration and went uncredited.
While the convey 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.