One main thread of the plot concerns Johnnie Rico’s conflict with his father, a successful businessman who objects to him joining the military. He leaves without his father’s blessing; much later, after he has become an officer, he learns that his father had done a complete turnaround. One day on his spaceship, Johnnie is amazed to see his father report to duty as a corporal. They sit down so his father can explain how he changed his ways and joined the military. His wife's death had been the wake-up call, so he sold and gave away the business and enlisted.

I had to perform an act of faith. I had to prove to myself that I was a man. Not just a producing-consuming economic animal . . . but a man.

Technical descriptions of futuristic military options abound in the novel. For example, in Heinlein’s future society, there is limited tactical use of small nuclear weapons. Johnnie describes how he launched one in a combat zone into which he had just parachuted.

I . . . raised the launcher to my shoulder, found the target and pulled the . . . trigger[s] . . . [M]y first rocket hit . . . [with] that unmistakable (if you’ve ever seen one) brilliance of an atomic explosion. It was just a peewee, of course, less than two kilotons nominal yield, with tamper and implosion squeeze to produce results from a less-than-critical mass—but then who wants to be bunk mates with a cosmic catastrophe?

Johnnie reflects back on the civics lessons he learned from Mr. Dubois. That teacher tried to instill in his students the idea of relative value so that they would appreciate effort as much as unearned benefits of their privileged lives. He told them,

The value of a thing is always relative to a particular person, is completely personal and different in quantity for each living human . . . This very personal relationship, "value," has two factors for a human being: first, what he can do with a thing, its use to him . . . and second, what he must do to get it, its cost to him.