Based on the famed W.W.II cartoons: Lowbrow G.I.s Willie and Joe, on the Italian front, are good soldiers in combat, but meet the antics of gung-ho Captain Johnson and other military snafus with a barrage of wry comments. On a 3-day pass in Naples, Joe's penchant for wine and women involves the pair with luscious Emi Rosso and her moonshiner father, whose tangled affairs land them in ever deeper trouble.

In 1943, on the Italian front outside Naples, reluctant but competent soldiers Willie and Joe avoid combat, instead reading pulp comics and taking naps. Meanwhile, Capt. Ralph Johnson picks fresh-faced recruit Albro Allen to accompany him on his first trip to the front. There, Johnson attempts to maintain his by-the-book leadership system, even though the troops are undermanned and under-supplied. He soon learns the folly of his ways, however, when he orders Willie and Joe fire at a nearby German battalion, disregarding their protests. With their position now revealed, they draw heavy fire and are forced to move the whole troop. They traipse to the closest village in an attempt to take it over, but are counter-attacked. After killing several snipers, Willie and Joe stumble into an abandoned bar. Joe finds a bottle of cognac and refuses to leave, and when the bar is bombed, Willie is evacuated and forced to leave Joe behind. Distraught, Willie returns to the camp, where he is teamed with Albro on a mission to determine where the German line starts. They find the Germans' foxholes and are about to turn back when Albro impulsively throws a grenade at the Germans and the two are attacked. They finally make it back to camp, where Willie hears that Joe has been found and transferred to a Naples hospital. Eager to retrieve his experienced partner, Willie asks Capt. Johnson for long-overdue leave, but is denied. Over the next days, however, Willie demonstrates his "combat exhaustion" by slipping up repeatedly, and is eventually granted leave. He rushes to Naples, but is immediately arrestd by M.P.s, who label his filthy non-regulation clothing as disgraceful. Willie then escapes to the hospital and disguises himself as a doctor to gain entrance into Joe's room. There Joe at first pretends to be badly hurt, but finally agrees to return to the front with his friend. Joe steals a fresh uniform and sneaks out of the hospital with Willie, but in the streets, Joe is robbed by an Italian child, Nino Rosso, and chases him. The chase draws the attention of the M.P.s, who follow the soldiers to Nino's apartment. Inside, Joe quickly forgives Nino when he sees the boy's beautiful older sister Emi. He flirts with her until the police rush in, and when Willie and Joe try to escape through the back room, they unwittingly expose Poppa Rosso's bootleg cognac mill. Everyone is arrested, but only the still-unkempt Willie is chastised by Maj. Lester, who commiserates with Joe about Willie's appearance and then calls the front to complain. His call is transferred to Col. Akeley, who condemns Lester for harassing his hard-working men and orders them released. Outside, Willie is furious with Joe for agreeing with Lester, and Joe begs his forgiveness by promising that he will accompany Willie to the front without delay. Moments later, however, Joe sees Emi, whose father is being held in jail, and stops to comfort her. The three go to a bar together and hours later emerge drunken and emotional. They sleep at Emi's, but when Willie awakens he is angry to discover that Joe has left to attend court all day with Emi. Willie chases him to the court, where they are both convinced to testify on the behalf of Poppa, who is on trial for bootlegging. During the trial, Willie points out that the police have not presented any physical evidence of a crime, and the judge is forced to throw out the case. As they are saying goodbye outside court, however, they notice a truck full of black market Army supplies in Poppa's driveway, and Joe insists that they drive it to the front to relieve their fellow soldiers. As soon as they leave the city, they are spotted by M.P.s and chased through the Italian countryside until they finally run out of gas. Maj. Lester arrests them, but when he puts gas in the truck and orders Willie and Joe to drive it back to Naples, they escape and race to the front. German soldiers see the truck, followed by scores of police cars, and assume they are being attacked. Soon after, Col. Akeley, who is desperate for supplies, is told that the Germans are mysteriously retreating. When Willie and Joe then pull up with the truck, he puts all the M.P.s to work in his troop, demotes Maj. Lester and decorates Willie and Joe, who find themselves filled with renewed fighting spirit.