SAN DIEGO — I don't need to read between the lines here on my computer screen in the MSN Messenger dialogue box. The meaning of my son's Instant Message is clear. He's worried. Worried he might not pass the test that would mean his promotion from specialist to sergeant.

It was only three years ago, after high school, that Roman signed on for a four-year stint in the Army. Not long after boot camp, he was sent to Iraq with the 1st Armored Division. At the beginning of that deployment, I'd addressed letters and packages to "Pvt. Diaz." By the end of his 15 months there, that title had changed to "Spc."

"Just do your best," I tap out on my keyboard. "And you'll do fine." A motherly mantra as familiar to him as "eat your vegetables" and "pick up your socks."

But he doesn't see it as that simple. And he tells me why. He'd been given a practice test this morning, and he blew it, he says, big time. With the real test less than 24 hours away, he seriously doubts he'll be earning an extra stripe anytime soon.

A bright kid who always coasted to good grades, Roman has never been fond of memorizing facts for multiple choice tests. And this is that kind of quiz. Specifics. Technical details. Map reading. Procedure following.

"If I don't pass tomorrow," he types, "I won't be able to try for sergeant again for another six months."

But to his way of thinking, that isn't the worst of it. If he doesn't make sergeant, he won't be allowed to continue leading the group he's actually been in charge of training for the past couple of months. His previous boots-on-the-ground experience in places like Baghdad and al-Kut had been, I think, a factor in his being given those responsibilities shortly after he was assigned to the 101st Airborne in Ft. Campbell, Ky., earlier this year. None of the other men in this new squad of his had ever been to war. But that's where the 101st will be heading a few weeks from now. Roman, too, along with the men he's nicknamed his "Jedi."

Unlike them, he knows what lies ahead. Knows from experience that being well trained can mean the difference between life and death. Physical fitness, for instance, matters greatly when you've got a 70-pound pack on your back, a 6-foot wall between you and cover, and insurgent bullets churning up the dust at your feet.