The Invisible Enemy

At fifteen he was sent to war to fight an enemy he couldn't understand. But more puzzling was the victory to be won—after he met defeat!
It was the day.
The automobile with its three passengers moved slowly along the quiet morning street. There was no need for hurry.
The boy's father was soberly recalling his own war experiences, wondering how similar Tom's would be. The mother was remembering vividly fragments of films, of facsimile reports, of forgotten conversations, envisioning her son cringing pathetically in a shallow foxhole as the penultimate weapon burst into grisly glory in the dark dawn sky. Tom's own thoughts were tense, but he managed to conceal his nervousness from his parents.
We're here, son, his father announced calmly, pulling the car up to the curb.
Dear, can't we drive around the block just once? his mother asked, her voice almost a whisper.
We're early.
No, mom, Tom said crisply. He opened the door and stepped out onto the sidewalk.
Want us to go in, son?
No thanks, Dad.
But we want to, Tom, his mother said. Of course, we'll go in!
There's no need for you to. I'm already registered, he told her. He reached out to grip his father's hand.