Stan Laurel and Oliver Hardy join the French Foreign Legion after Ollie's sweetheart Jeanie-Weenie (only ever seen as a photograph) rejects him, as it is the only place where Ollie can forget her. When they arrive at the barracks in French Algeria, they discover that not only are the other soldiers trying to forget lost loves, their lost loves all happen to be the one and the same woman Ollie is trying to forget: Jeanie-Weenie!
During World War I, two American Doughboys, Tommy Turner and Gilbert Simpson, are more interested in picking up girls than in military duty. In Paris, they go AWOL in order to follow their libertine pursuits. They alternate between impersonating officers in order to impress the ladies, and avoiding being found out by the military police. During their hijinks, the pair accidentally steal the Colonel Marshall's car (their commanding officer), which is were Tommy meets and falls in love with Annette, who unbeknownst to him is Colonel Marshall's younger daughter.
Elmer (Keaton), a member of the idle rich, is smitten by working girl Mary (Sally Eilers), who will have nothing to do with him. When Elmer's chauffeur gets caught up in an army recruitment drive and quits, Elmer goes to an employment agency to find a new driver and accidentally enlists in the army. Elmer learns that Mary is on the base to entertain the troops and learns that his drill sergeant, Brophy (Edward Brophy), is also interested in Mary.
Flagg (Victor McLaglen) and Quirt (Edmund Lowe) find themselves transferred from Russia to Brooklyn to South America, in each place squaring off over a local beauty.
Slow-witted army private Cuthbert Hope (Laurel) manages to makes life miserable for his gruff Top Sergeant Banner (Hardy). Banner must also report back to firm Captain Bustle (Jimmy Finlayson).
Flagg and Quirt are veteran United States Marines sergeants whose rivalry dates back a number of years. Flagg is commissioned a Captain, he is in command of a company on the front lines of France during World War I. Sergeant Quirt is assigned to Flagg's unit as the senior non-commissioned officer. Flagg and Quirt quickly resume their rivalry, which this time takes its form over the affections of Charmaine, the daughter of the local innkeeper. However, Charmaine's desire for a husband and the reality of war give the two men a common cause.
In 1924, "Skeet" Burns applies to join the United States Marine Corps, but only to get a free train ride to San Diego, California. When he arrives, he escapes from veteran Marine Sergeant O'Hara and boards another train to "Tia Juana", Mexico for the horse races. However, upon his return, he enlists after all and comes under O'Hara's charge.
Isadore Goldberg, an enterprising Russian Jew, comes to the United States and establishes himself in the delicatessen business so that he can one day send for his parents. Forced to vacate his store, Izzy relocates in an Irish neighborhood; there, after he changes his surname to "Murphy," his business prospers. While waiting for a subway train, Izzy recovers a girl's handkerchief; later, he meets her in his store and learns that she is Eileen Cohannigan, from whose father he buys foodstuffs. After the arrival of Izzy's parents, he embarks for France with an all-Irish regiment and inspires his comrades to deeds of valor. He is welcomed home by Cohannigan, but when Cohannigan learns that he is Jewish, he denounces his daughter for loving him. With the aid of his service buddies, however, Izzy and Eileen head for City Hall to be married.