Bart joins the army after recruiters visit the school, so Homer takes his place. After he escapes with all the other soldiers, the colonel invades Springfield in a hunt to locate him.
After two army recruiters fail to recruit Jimbo, Dolph and Kearney, who are working in a shoe store in the mall (where Bart and Milhouse go to torture the bullies, and are later beaten up when the bullies' boss resigns from his job), they realize that the teenagers of Springfield are too smart to want to join the army, so they visit Springfield Elementary School to trick kids into signing Delayed Entry Program so that upon reaching the age of majority, they will automatically be enlisted.
An excited Bart comes home from school and shows Homer and Marge his preenlistment form. Marge is appalled at the idea of Bart joining the Army when he turns 18, so she sends Homer down to the army recruitment center to make them cancel Bart's preenlistment. Homer forces the two army recruiters to tear up Bart's preenlistment contract, but the army recruiters convince him to join the army instead. The next morning, Homer is shipped off to Fort Clinton, where they undergo rigorous exercises (except Homer, as apparently his "punishment" for acting like a clown involved eating donuts while watching his fellow soldiers do push-ups and having his feet massaged).
At the post, Homer infuriates the colonel. While the majority of recruits are assigned to the frontline infantry (including Rainier Wolfcastle, who was told he would be making recruitment films), Homer is assigned to OPFOR during the army's war games, along with the other recruits considered too stupid to be cannon-fodder. At the war games, the army uses live ammo instead of blanks, with the intent of actually killing them. Homer, thinking it's Chinese New Year, accidentally exposes his unit's location by launching a flare which blinds the soldiers, who are wearing night vision goggles.
Homer and his unit soon escape into Springfield with the army close behind. The colonel orders his troops to invade the town, thanks to leverage from the National Broccoli Day proclamation. The army declares martial law in Springfield. Homer's unit hides in Moe's Tavern, but Moe betrays them in exchange for a large wad of cash. Homer escapes through a manhole in the floor of the basement and makes his way to his own home, although the rest of his unit is captured. Soon, he is pursued through the house by a UAV until he blows it up in a closet in a scene reminiscent of the Looney Tunes gags. The Colonel then begins to round up and detain all men who are fat, or bald, or have ever been amused by the "antics" of Homer. This includes Jeffery Albertson, Barney Gumble and Superintendent Chalmers, who states that he's only balding. Because of the roundups, Homer hides out at the Retirement Castle and is forced to listen to Grandpa talk about anyone else's relatives.
Marge rallies the Springfield community with a phone tree to coordinate resistance to the occupiers in order to make a plan. The citizens spike the town reservoir with alcohol, intoxicating the occupying force. The colonel's resulting hangover is so great that he reluctantly surrenders to the townsfolk, stipulating only that Homer finish his enlistment. Homer does so by becoming a recruiter at the Springfield Mall, but doesn't get much success.
Robert Canning of IGN panned the episode, calling it "painfully unfunny" and claiming that the show's "attempt to satirize the state of the U.S. military simply crossed the line of good taste". He concluded that it was "by far" the worst episode of the season, and "quite possibly" the worst episode of The Simpsons. However, Canning praised the episode's Looney Tunes homage.