Jimmy Davis, as imagined by the screenwriters if not the novelist, demonstrates this thesis. A mild mannered draftee during the Great War, he faints at the prospect merely of sticking his bayonet into a practice dummy during basic training. Someone like this, the film says, has no business fighting a war, yet he was taken by conscription and sent to Europe, where his buddy the carny barker Fred Willis (Spencer Tracy, nearly typecast after Dante's Inferno) looks after him. Jimmy's war is part Full Metal Jacket, part Saving Private Ryan. Like Kubrick's Pvt. Pyle, Jimmy finds that marksmanship is the one thing he's good at, and he starts to feel fond of his weapon. He becomes a super sniper, but before his moment of grace undergoes an ordeal of cowardice. Stumbling upon a dead German while climbing a flight of stairs, Jimmy mistakes the corpse for a live soldier drawing a bead on him and instantly surrenders. Realizing his error, he ascends and finds he has a perfect nest to annihilate an enemy machine gun position. Gleefully he takes the Germans out one by one before his own position is blasted.
As Jimmy recovers, the romantic triangle plot kicks in. Jimmy and Fred are fond of the same nurse, the hard-boiled Rose Duffy (Gladys George). She prefers Fred despite giving him a lot of sass and a little physical abuse, but he goes missing during a big offensive while Jimmy's recovering. By the time Fred returns, having been a P.O.W., Jimmy and Rose are engaged. Fred can tell that Rose will dump Jimmy if he says so, but he also sees that Jimmy is too psychologically fragile to stand the loss. It's time for some pathos of renunciation as Fred lies to Rose about a wife and kids at home and earns her hatred for seemingly having strung her along.
According to one review I've read, Cowen's novel describes in detail Jimmy's troubles readjusting to civilian life, perhaps portraying him as a Forgotten Man driven to crime by the lack of other opportunities. The movie skips directly to Fred's rediscovery of Jimmy, who has an office in a building from which a sniper has just shot a gangster to death. The coincidence makes Fred, who now runs his own circus, suspicious, but Mrs. Rose Davis takes her husband as what he claims to be, a now-successful businessman. Inevitably, with Fred hanging around again, she grows suspicious of Jimmy, visits his office after hours and finds him plotting a St. Valentines style massacre with killers in cop uniforms. She rats him out and he goes to jail. He pleads guilty to keep his gang from whacking her and appears determined to go straight, but a fellow con goads him into a breakout. Jimmy tracks Rose to Fred's circus and demands that she go on the lam with him. She's willing as a matter of wifely duty but Fred's having none of it. He dares Jimmy to shoot him, asserting his own dominance by pretty much telling him he's nothing without a gun -- and Jimmy buys it, since Fred's always talked straight to him. He also figures out the score between Fred and Rose, which leaves him one honorable thing to do....
The film's final lines try to nail it down as an antiwar film. One of the cops hunting Jimmy is his and Fred's old drill instructor, to whom Fred says of Jimmy, "You oughta pin a medal on him. He was your prize pupil." This seems unfair, if only because the soldier/cop hasn't been a big enough character in the story. It may also muddle things, especially to more modern viewers for whom guns alone may suffice to explain Jimmy's tragic career, without bringing the military into it. Moreover, Cowen's original argument seems to have been that the system as a whole, in peace as well as war, deformed Jimmy by turning him into a killing machine only to kick him to the curb when it didn't need killers anymore. By leaving out Jimmy's pre-crime efforts to readjust, the movie makes it look like he made a beeline to crime and makes him look more like a villain than the victim it claims him to be at the end. The movie's real problem is that it needs to be Jimmy's story, but we mostly get Jimmy from Fred's point of view. The fact that Fred emerges from the war unscathed further undermines the closing argument that militarism mutated Jimmy into the monster Fred discovers in civilian life. Above all, the fait accompli that forces us to accept that misfit Jimmy has become a powerful gangster without seeing his ascent is deeply unconvincing, Franchot Tone being no more plausible in this respect than Jimmy Stewart might have been. In simplest terms the movie tries to explain too much and leaves too much unexplained. Since 1937 is still early in the "Code Enforcement" era, the filmmakers may have gone out of their way to steer clear of anything that might have looked like "glorifying" crime while portraying Jimmy's rise to power. Yet They Gave Him a Gun reminds us that the Code Enforcement (or "Classic") era was not a monolithic period of consistent rules. Not long after 1937 no one would have dared suggest that anyone's personality could be warped by the military giving him a gun. From the vantage point of World War II, 1937 looks like a period of relative freedom in movies, however it looks in comparison to Pre-Code Cinema. They Gave Him a Gun may be a failure, but Metro deserves some credit for taking a chance on an ambitious subject.