When your eyes adjust to dark places, you can see a lesson of survival. Straight from high school, I went into the Marine Corps, and with other young Marines of my day I poked my nose into some of the toughest saloons along the U.S. West Coast and in five countries of Asia straight-shot jukebox dives where trouble kept an open tab.

Again and again, I watched as stray sparks gathered over some perceived or real slight between trained killers who fed off military rivalries, testosterone and the fatalism of wartime. Voices roared, stools toppled onto the floor as men took to their feet and everyone in the room tensed. Then, at the instant of certain ignition, these explosions almost always fizzled.

What looked terrifyingly like reckless bravado was, in fact, bluff. Not the kind of polite bluffing people use in poker. This was different. These Marines were edgy, wild, theatrical bluffers. They avoided trouble for the most part by seeming ready, even eager, for it. Like all good bluffers, they had to convince you they weren’t.

Marines were supposed to be just a little nuts anyway, and that fellow who just bumped you with an elbow might be one of those with a knife in his boot. Standing up to him meant conveying that you might be every bit as dangerous or more so. Primeval, you say? OK, but no less real.

Humans have yet to outgrow their history. As the poet John Dryden observed, “Peace itself is war in masquerade.” Enlarge this approach to a grand scale. We can call it the new national security strategy of the United States, as spelled out, in word and deed, by the Bush administration.

Unsettling? Hugely. Hazardous? Without a doubt. Effective? Possibly.

In the Marines, you could steer clear of this kind of trouble by staying home at night. But that’s no longer an option for the United States.

I’m no foreign-policy scholar, but I’ve spent enough time overseas in trouble spots to have lost my hope in reason and good will. Hoping to sit down and work things out when the other fellow is drunk, whether on whiskey or fanaticism, amounts to wishful thinking. Tensions in much of the world today resemble those in a sweaty, back-alley saloon more than those in an air-conditioned conference room.

In this face-off with Iraq, President Bush has flat-out convinced me, and most of the rest of the world, that he’s not bluffing which is essential to pulling off any good bluff. I’m with those who think he’s thirsty for this fight. Some people accept that it’s for the sake of U.S. security. Others figure he’s out to settle an old family score or to distract voters from the shaky economy. You pick it, he’s made himself scary.

From what I’ve seen of the modern world, that’s a tactic with a fair chance of getting you through tight spots with your teeth intact. I suspect Saddam Hussein is having trouble holding down his dinner.

On the other hand, when you’ve watched enough of these blustery encounters, you realize that it’s a thin, shifty line sometimes so thin you can’t see it between standing up for yourself and being a bully.

That accounts for all these questions at home and the storm of doubts abroad. Why this face-off just now? (Has something changed in the last 12 months?) Why this target? (Which nation harbors more terrorists and has brought the world closer to a nuclear exchange, Pakistan or Iraq?) More to the point, why aren’t the answers more convincing?

Bush’s new national security directive and his relentless war drums proclaim a prerogative for the United States: the right to act pre-emptively and unilaterally. In practice, there’s not much new here. Think Grenada or Panama, to name two. But now it’s in writing for all the world to chew over, and Bush has taken to his feet to show what it means.

If he can pull off his bluff, if he can inspire resolve in the United Nations and it’s foolish to discount these possibilities the United States will have stood down a tyrant and instilled in the civilized family of nations new confidence in countering fanaticism.

But if he cannot, then there is more to win than a fight along the Euphrates. Pulverizing a downtrodden foe proves one’s might. But to quiet the murmurs of onlookers, Americans have to show that we’re right too.

We’re not just professing ideals, we must live up to them in this new kind of war against terrorists. That you can’t bluff.