First things first, it's pronounced "bird" like those flying animals. Jamie meets Sergeant Byrd at the rec center, where she learns how to develop film. It's through Byrd that Jamie realizes war is a lot different in real life than in the movies. Sure, he teaches her all kinds of army traditions and Vietnamese words—without him, she wouldn't know that you need a bac-si (ahem, medic) or glad bag (body bag) if you're injured in Vietnam—but it's what he doesn't say that sticks with her. Byrd doesn't even want to develop his three hundred rolls of film from the war because he's afraid of reliving it.
In fact, he already does in his nightmares. Jamie tells us:
I remembered something that Sgt. Byrd had told me, that he dreamed about Vietnam almost every night, and some nights he woke up to find himself crouched in the dark between the bunks in his barracks, his whole body alert, listening. (10.31)
Doesn't sound like fun to us. He's plagued by what he saw over there, which makes Jamie think war might not be very much fun. Gee, who would have thought?
We can see why Byrd would just as soon forget the past, but it keeps creeping back into his life now. It's only from hearing bits in pieces about Byrd's horrific experiences fighting in Vietnam that it dawns on Jamie that war is not a game.