The film recounts the formation, training, and first mission of the 1st Special Service Force, a joint American-Canadian commando unit, known as the Devil's Brigade.

The film dramatizes the Brigade's first mission in the Italian Campaign, the task of capturing what is considered an impregnable German mountain stronghold, Monte la Difensa.

[3] In the summer of 1942, American Lieutenant Colonel Robert T. Frederick, a War Department staff officer with no prior combat or command experience, is summoned to Britain where he is selected by Admiral Lord Louis Mountbatten to raise a commando force composed of both American and Canadian personnel for operations in German-occupied Norway.

Back in the U.S., Frederick arrives at the derelict Fort William Henry Harrison in Montana where he receives his American troops — all of whom are jailbirds, ne'er-do-wells, and misfits.

Frederick remains undeterred and manages to persuade Lieutenant General Mark Clark to give his men a chance to prove themselves with a new mission in Italy.

Facing severe obstacles, the Devil's Brigade attacks the undefended eastern side of the mountain by scaling a cliff the Germans believed could not be climbed.

The film makes much of the initial animosity and rivalry between contrasting (and stereotypical) Canadian and American personas until the men forge themselves into a cohesive unit focused against the German enemy forces.

[14][failed verification] However, the birthday scene which is set in Italy was filmed at the National Guard Armory in Salt Lake City, with Brigham Young University students as extras.

[11] Wolper had the Brigade wear attractive but fictional red berets that appeared as well as on the film's posters and on the tie-in paperback cover of Adelman and Walton's book.

The cast of The Devil's Brigade included NFL running back Paul Hornung and World Middleweight Champion boxer Gene Fullmer in minor roles.

The album was illustrated with the original Sandy Kossin artwork of the film and featured instrumental (with whistling) and a male chorus singing lyrics to North's title theme.

In 2007 Film Score Monthly and Intrada released a limited CD edition of North's original score with Kossin's artwork including alternate versions of the title theme, North's own arrangements of four 1940s jazz popular tunes, two traditional Christmas carols, and the pipe band version of Scotland the Brave featuring in the film.

Canadian military historian and writer Tim Cook said of the film “It is a rousing wartime adventure that I find repays with each viewing.