Mixing fictional characters with true ones, Irish Americans train and fight in the world war as a loud-mouth discovers he is cowardly under fire.
In 1917 at a U.S. Army training camp Major Wild Bill Donovan (George Brent) swears in new recruits. Wise-cracking Jerry Plunkett (James Cagney) is put on report but keeps irritating others. Sergeant Mike Wynn (Alan Hale) drills men and shows how to bayonet. Poet Joyce Kilmer (Jeffrey Lynn) signs a book for Lt. Ames (Dennis Morgan). Arguing over the Civil War, the Irish 69th fights the 4th Alabama. Donovan says Americans fought but became one people, and he has a rainbow division. Donovan tells Father Duffy (Pat O'Brien) they need tough training to face experienced soldiers. Father Duffy prays.
They ship out and march in France. Duffy counsels Plunkett for being a troublemaker. Men sing Christmas carols in church as Duffy prays. Plunkett looks in and walks out. They march in snow, and Crepe-Hanger Burke (Frank McHugh) picks up a duck. Kilmer helps a suffering soldier and composes a poem. A colonel (Henry O'Neill) orders the majors into combat. Mike warns Plunkett about flares in the trench; but Plunkett sends up a flare and throws a grenade, causing their men to be killed. Plunkett runs away until Lt. John Wynn (Dick Foran) stops him. At a funeral Kilmer recites a poem. Plunkett takes off guard duty for a beer, but Mike catches him. They fight, and Mike hits Plunkett. When Donovan arrives, Plunkett says Mike did not hit him. Donovan calls in Plunkett for a transfer but says Duffy wants to give him another chance.
In the next battle Duffy calms Plunkett, who feels like running again. Donovan calls for volunteers to intercept a German patrol and picks Plunkett too. Kilmer keeps Plunkett from running but is killed. Ames and Duffy attack Germans, and Ames is killed protecting Duffy. Timmy Wynn (William Lundigan) was also killed because of Plunkett. Duffy tells Donovan that Plunkett should not be executed, but Donovan disagrees. Plunkett asks Duffy to help him escape, but Duffy says no. Dying Mike Murphy (Sammy Cohen) is Jewish but asks Duffy to pray. During bombing Duffy urges Plunkett to help his regiment. Plunkett rescues Duffy, who re-assures the men and prays. Plunkett runs out. Donovan leads men advancing. Plunkett asks Mike how to fire mortars. Plunkett launches them and jumps on a grenade to save Mike. Wounded Plunkett calls on Duffy and gets the last rites as Mike honors him. In the final scene soldiers march home, and the spirit of Duffy, who died in 1932, prays for them and for peace.
Donovan, Kilmer, and Duffy were based on real people
in this unabashed propaganda film aimed at preparing Americans
for another world war against Germany that nonetheless reveals
the horrors of war, the importance of discipline for military
success, and the ultimate refuge of religion.