Tyler Boudreau is bicycling across the United States to talk about war, and he says he really does want to talk, not lecture.

The former Marine Corps captain fought in Iraq and later resigned his commission because of his mounting disillusion with the war. He said he is sometimes accused of preaching to the choir when he meets with mostly anti-war audiences.

"For one thing, I'm not preaching," he said, "and for another, I'm not sure the choir has it all down."

Boudreau, 38, said most veterans have experienced the "difficult, ambiguous" nature of war and tend to have mixed feelings on the subject. It's the people who haven't seen war, who view it as an abstraction that happens to someone else, who hold unyielding opinions.

For too many people, whether pro-war or anti-war, he said, "everything's black and white and nobody's talking about the complexities."

The complexities in Boudreau's case include these: He was a Marine with a "craving for war" and an intense desire to lead men into battle. His opposition to the war in Iraq grew out of a tactical analysis of the way it was being fought.

As he explains in his memoir, "Packing Inferno: The Unmaking of a Marine," U.S. troops were sent to Iraq with the mission of stabilizing the country and establishing good relations with the Iraqi people. But as the Marines began taking casualties, particularly from the hated roadside bombs, the focus shifted to raids and patrols - combat operations.

Boudreau said his break with the Marines grew out of his deep affection for the men under his command. He couldn't disobey a direct order, but the futility of sending Marines out on patrol, exposing them to attacks for no reason but to show that the Americans controlled the roads, led him to save lives by subterfuge.

His unit was shorthanded, so if he found something else the troops "needed" to do, he could get a patrol canceled and potentially buy some young Marine another day.

Boudreau was a Marine for 12 years and served in Iraq in 2004. In April 2005, before he was to be redeployed to Iraq, he gave up command of a rifle company and resigned his commission. He wrote his memoir as a chronicle of his coming to grips with his time as a Marine and his thoughts on the meaning and consequences of war.

He is bicycling from Seattle to Northampton, Mass., his hometown, by himself, though some people have joined him for short legs of the cross-country trip. He stops wherever people want to meet with him. His two most recent events were in Missoula and Helena, which is where I caught up with him by phone. He'll be in Billings Tuesday and will give a free presentation at 7 that night in the Unitarian Universalist Fellowship Billings, 2032 Central Ave.

Boudreau said he begins most of his discussion sessions by talking about his life and his experiences as a Marine and then lets the conversation go where his listeners want to take it. He says he is not an expert on the military, history or politics.

"What I am an expert on is my own experience and my own history," he said.

His goal is not to change people's minds or to persuade them to agree with his conclusions about war in general or the war in Iraq. He wants to show people, through his experiences, how he came to those conclusions. Understanding how somebody else came to believe something is a powerful way to move a discussion beyond superficialities and into deeper waters, he said.

He also wants to talk about post-traumatic stress. He intentionally leaves off the word "disorder" that is part of the usual phrase, arguing that the term reduces veterans to powerless victims.

He also objects to the notion that post-traumatic stress is always the result of witnessing a violent or horrific incident. The standard diagnosis fails to acknowledge that sometimes post-traumatic stress is brought on by guilt, suffered by soldiers who can't reconcile civilian morality with the morality of war.

Omit "disorder," he writes in "Packing Inferno," and "Suddenly the veteran's distress can be viewed as the product of a good quality, not a bad one; and I think that would be valuable for wounded veterans to feel: that their distress is a good thing and natural."

Boudreau doesn't want people to think that his bicycle tour is his "little homespun remedy for post-traumatic stress." That is something he dealt with before the trip began. He's biking because he wanted to talk and listen and connect with people, and to probe his own thoughts about important subjects.

And he simply wanted to get to know the United States better.

"We always talk about defending our country," he said, "but most of us haven't seen a tenth of it."