The film was subtitled "Project 6,000; Information Film #1." In an onscreen foreword, the purpose of the Why We Fight series is stated through a quotation of G. C. Marshall, Chief of Staff: "This film, the first of a series, has been prepared by the War Department to acquaint members of the Army with factual information as to the causes, the events leading up to our entry into the war and the principles for which we are fighting. A knowledge of these facts is an indispensable part of military training and merits the thoughtful consideration of every American soldier. We are determined that before the sun sets on this terrible struggle, our flag will be recognized throughout the world as a symbol of freedom on the one hand, of overwhelming power on the other. No compromise is possible and the victory of the democracies can only be complete with utter defeat of the war machine of Germany and Japan." The last half of the final sentence is repeated at the end of the film, and is followed by the "V for Victory" symbol.
       According to documents at NARS, work began on the film's scenario on 1 Apr 1942, and a first answer print was submitted for approval on 20 Oct 1942. While most of the film was taken from newsreels, Hollywood studio libraries, government footage and film supplied from British and Russian sources, portions were shot for the production by Maj. Anatole Litvak at the Twentieth Century-Fox studios, by Robert Flaherty for the Capra Unit, and by Consolidated Film Industries. The animated maps were made by Walt Disney Productions. The musical score consisted of fifty compositions, many of them familiar tunes such as "The Caissons Go Rolling Along," "Hail Columbia," the Fascist hymn "Giovinezza," "Ave Maria," "A Hot Time in the Old Town Tonight" and "Onward Christian Soldiers." According to Capra's autobiography, Alfred Newman wrote and recorded the score at Fox without charge.
       According to modern sources, the picture was first shown on 30 Oct 1942, and by May 1943 had already been seen by millions of troops in camps and overseas, and was well received everywhere it played. According to a contemporary Time article, the favorable reactions of Elmer Davis of the OWI and President Franklin Roosevelt led to the decision to release the picture theatrically. However, the release was blocked for months by Lowell Mellett and Nelson Poynter of the Motion Picture Bureau of OWI. The War Activities Committee of the Motion Picture Industry also cooperated reluctantly. According to FD, special negotiations were required at OWI to arrange the release, with 150 prints to be made available by OWI free of charge with the industry bearing distribution expenses. Some prints were dubbed in French, Spanish and Chinese, according to NARS records. Keystone Broadcasting System gave 1,000 hours of air time to plug the film over a month's time. All copyright owners holding the rights to scenes used in the film gave permission for the theatrical release.
       According to This Week, soldiers liked the film and believed it "explained why they were fighting the war." HR noted that the audience reaction at its first public showing was sharply divided, with some applauding, and others walking out, dismissing the movie as propaganda. Reviewers praised the film but complained that it was outdated, incomplete and not as compelling as OWI's The World at War, released eight months earlier. Public reaction was expected to determine the release of the remaining films in the series. According to modern sources, the film did poorly, but the lack of commercial success was not a deterrent to the theatrical release of a number of other government-sponsored war documentaries (See Entry for The World at War for more information on overlapping subject matter of government film production units). Of the remaining feature-length films produced by the Capra unit, only The Battle of Russia, The Negro Soldier and Tunisian Victory received theatrical releases. Prelude to War was one of two feature-length films to win an Academy Award as Best Documentary of 1943, and it also won an award from the National Board of Review. Modern sources erroneously credit Dimitri Tiomkin with music.