Bart gets into a fight with Nelson, the school bully, for protecting Lisa's cupcakes. Nelson beats him up after school, and vows to continue to beat him up every day.
Bart turns to Grampa, who takes him too see Herman, an army veteran who runs a military supplies store. Herman helps him build and train an army of kids in the neighborhood.
Bart confronts Nelson, and unleashes his army, who pelt Nelson with water balloons. He is tied up and must sign a treaty, promising never to beat up kids again.