Willie (Ewell) and Joe (Lembeck) are two U.S. Army veterans of World War II who got through the war by Goldbricking. After returning to civilian life they are recalled to active duty and end up part of the post war occupation forces in Japan. Chaos ensues as they attempt one con job after another in order to avoid work details and get leave to spend time in Tokyo.
In Korea, AD 668. Kim Beob-min (Hwang Jung-min) is the king of the small southern Korean state of Shilla and makes a deal with China's Tang dynasty officials to have a combined strike against the larger northern Korean state of Goguryeo. The conditions of the agreement involve Shilla being given back the Korean state of Baekje. The combined troops march to Pyongyang Castle, where Goguryeo's Yeon Gaesomun (Lee Won-jong) dies and hands over command of the army to his second son Yeon Nam-geon (Ryu Seung-ryong). This action upsets his first son, Yeon Namsaeng (Yoon Je-moon) who is not as war-hungry as Nam-geon.
The story centers on Eugene Morris Jerome, a 20-year-old Jewish Brooklynite who is drafted into the United States Army during the last year of World War II and is sent to Biloxi, Mississippi for basic training. While there he learns to cope with fellow soldiers from all walks of life, falls in love, and loses his virginity in less than ideal circumstances, all while having to cope with an eccentric drill instructor.
The Stooges are street peddler greeting card salesmen who anger a man on the street after an accidental altercation. They are then approached by a woman (Evelyn Young) with a request to help her make her evil man-hating husband (Richard Fiske) jealous. Realizing it the same man they faced before, the Stooges defend themselves against the irate husband with their usual combatives and flee from the husband shouting his threats. In hiding from him, they line up on a queue that takes them to a recruitment office by mistake and end up joining the army.
The military is performing a practice air raid on New York City. Sach convinces the boys that it is real and they go down to the recruiter's office and enlist. Meanwhile, Slip arrives at Louie's and finds out what just happened and goes down there to stop them. He is too late, as they have already joined, and is tricked into enlisting himself.
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.
U.S. Army Specialist 5 (SP5) Tulsa McLean (Elvis Presley) is a tank crewman with a singing career. Serving with the 3rd Armored "Spearhead" Division in West Germany, McLean dreams of running his own nightclub when he leaves the army, but such dreams don't come cheap. Tulsa and his buddies have formed a band and perform in various German "Gasthauses", night clubs, and on an Armed Forces stage. In one bar, he even discovers the record "Blue Suede Shoes" sung by someone named Elvis Presley on a jukebox.
Ex-Marines Jimmy McGinnis (Victor McLaglen) and Harry Curtis (Edmund Lowe), who haven't seen each other for fifteen years, meet at a racetrack. They both immediately drop their jobs as an attendant and cleaner to rekindle their friendship and brawl over which one will have Violet (Binnie Barnes) for their girl. When visiting a clip joint called the Shoreleave Cafe with Violet, they meet the owner, Jim Blake (Paul Kelly). Blake was their former captain; he left the Corps under a cloud when he was blamed for a security breach. Blake is involved in espionage, arranging to buy the plans for a new amphibious vehicle.
Captain Yossarian (Alan Arkin), a U.S. Army Air Force B-25 bombardier, is stationed on the Mediterranean base on Pianosa during World War II. Along with his squadron members, Yossarian is committed to flying dangerous missions, and after watching friends die, he seeks a means of escape.
During World War II, the young undergraduate Stanley Windrush (Ian Carmichael), is conscripted into the British Army. Unlike his friend Egan (Peter Jones), Windrush is a most reluctant soldier and struggles through basic training at Gravestone Barracks. Failing his officer selection board, he is posted to a holding unit, under the command of Major Hitchcock (Terry-Thomas). Most of the soldiers there are malingerers and drop-outs.
Charlie is in boot camp in the "awkward squad." Once in France he gets no letters from home. He finally gets a package containing limburger cheese which requires a gas mask and which he throws over into the German trench. He goes "over the top" and captures thirteen Germans ("I surrounded them"), then volunteers to wander through the German lines disguised as a tree trunk. With the help of a French girl he captures the Kaiser and the Crown Prince and is given a statue and victory parade in New York and then ... fellow soldiers wake him from his dream.
The boys' friend, Dave Moreno, is being held for treason by the U.S. Air Force. Slip and Sach go to headquarters to help Dave, but mistakenly enlist. Sach is also mistakenly assigned to a WAF barracks. When the boys finally do visit Dave he tells them he does not need help, as he is secretly being used to capture enemy agents. Undeterred by Dave's words, the boys continue to investigate and Slip and Sach wind up airborne. Good luck allows them to land safely, just where the spies are hiding out. They capture the spies and Dave's true mission is revealed.
Nick Moroni (Remo Germani), a young singer called up, learns that his wife Catherine (Alicia Brandet) from which separate lives, is about to leave for America bringing with her the son born of their union; so he abducts the baby and takes him to the police station, charging the soldier Piscitello (Franco Franchi) to keep him well hidden. The terrible sergeant Camilloni (Ciccio Ingrassia), discovers the child and is led to believe that he left him a woman with whom he had an affair in the past and, convinced that he is the father of the creature, asks Piscitello to keep he hidden from the eyes of all. Piscitello naturally takes advantage of the situation to blackmail the sergeant, demanding concessions to no end and subjecting him to harassment of any kind .