Our Marine platoon stayed up late to listen on a hand-cranked shortwave radio as Colin Powell testified before the United Nations about Iraq’s weapons of mass destruction. It was February 2003, and we were camped in the northern Kuwaiti desert, awaiting orders to invade Iraq.

The prospect of being “slimed” — and having to battle through a chemical attack — dominated every part of our planning. We wore heavy charcoal suits to protect us from chemicals, taped nerve-agent-detection paper to the windshields of our vehicles, and practiced jabbing antidote needles into our thighs.

We made bets not on whether it would happen, but when. We didn’t know what line we had to cross to provoke Saddam Hussein into using weapons of mass destruction — maybe the border, the Euphrates, the Tigris or the doorway to his presidential palace — and so the overriding objective was speed: get to Baghdad and cut the head off the snake.

Our conviction was strengthened on the second day of the war, when we interrogated an Iraqi officer found carrying a gas mask, rubber gloves and nerve agent antidotes. Did he really believe we would use chemical weapons against Iraq? No, he replied, but he expected that Saddam Hussein would use them against us, and his unit would be caught in the cross-fire.

This deception twisted our priorities dangerously out of whack. Methodically clearing areas of enemy fighters, and then securing them to protect the populace, seemed like a risky luxury in March and April. By August, with the insurgency in bloom, it had become a colossal missed opportunity.

The weapons, we now know, were some combination of relic, bluster and ruse. We focused on the nerve-agent feint, and got roundhoused by the insurgent hook. I wish we could all go back to those nights in the Kuwaiti desert, when a more sober assessment could have changed the way we fought, and maybe lessened the likelihood that we’d still be fighting five years later.

Nathaniel Fick is a fellow at the Center for a New American Security and the author of “One Bullet Away: The Making of a Marine Officer.”