Paul Verhoeven’s version of “Starship Troopers” devotes significant screen time to exploring why Rico fights in the service. In the film, Rico becomes jealous of a rival athlete who’s enlisting, and has been flirting with his girlfriend Carmen. To impress her, Rico enlists on a whim, but that’s not at all how it goes down in the book.
As the story begins in Heinlein’s novel, Rico is actually prompted to enlist after his friend Carl announces his intention to sign up. In the book, Carl and Rico are described early on as the best of friends, having grown up doing everything together. Rico has second thoughts after his father attempts to bribe him with a vacation to Mars, though when he hears that Carmen is going too, he finally makes up his mind. Like the movie, Rico has a crisis of confidence while in boot camp.
In the book, after a disturbing incident that sees a fellow recruit court-martialed and flogged, Rico wants to quit his training. But unlike in the movie, where the attack by the Arachnids kills his family and convinces him to stay, it’s something else entirely that prompts him. Here, it’s a heartfelt letter received from his old teacher, Mr. Dubois, who has heard he’s joined up and expresses how proud he is. Emboldened, he sticks with it, gets over the hump, and serves in the mobile infantry with distinction.