The two soldiers followed standard rules of engagement as a suspicious truck rolled toward their convoy in Iraq.

First, they fired a warning flare. But the truck kept coming. Then, a warning shot with live ammunition. The truck kept coming.

Then, they took aim at the driver, shooting and killing him.

Yet when they searched the vehicle, they found no weapons or bombs around the dead man.

Soon, they were sitting with Minnesota National Guard chaplain Steve Timm, anguishing over whether they had committed an unforgivable sin that violated their Christian beliefs.

"It's really, really tough," Timm said, "to believe that God hates you."

Those kinds of deadly wartime encounters — and their imprints on soldiers' consciences — are the focus of a new movement among military medical researchers to study "moral injuries," the invisible scars on soldiers who believe they have committed condemnable acts.

Psychologists at the VA Medical Center in Minneapolis are at the forefront of the work, helping to define moral injury, examining how it aggravates mental disorders, and testing whether an experimental form of group therapy can heal such wounds of the spirit.

A study of survey results for 814 Minnesota National Guard members who served in Iraq over the past decade showed that those who experienced moral injury had higher levels of depression and post-traumatic stress disorder (PTSD).

Moral injury generally refers to any type of guilt, shame, or depression that arises from actions that may have violated deeply held beliefs. But for this study, which was presented at the Minneapolis VA Medical Center last month, soldiers met the criteria if they killed in combat, felt their actions were unforgivable, and believed that God had abandoned them.

The lack of resiliency among soldiers who met this definition was alarming, said Dr. Irene Harris, the VA psychologist leading the research. "Basically, [they feel] at my spiritual functioning level, I don't think I belong here in the world. I'm not worth it. I have a sense that I should not be here.''

The moral consequences of war on the individual psyche have been examined for centuries; the ancient Indian poem Mahabharata and the 4th-century writings of St. Augustine asked when warriors were justified in killing and warfare.

The term moral injury wasn't outlined until 2009, though, when researchers at the VA's National Center for PTSD in Boston found evidence of long-lasting impairment in soldiers who had used lethal force or participated in wartime atrocities.

Moral injury doesn't always result from acts committed, Harris said. In some cases, inaction can leave equally deep scars.

Timothy Doble is a peer support volunteer at the Minneapolis VA who uses his experience as a Vietnam vet to support other veterans experiencing mental health challenges. Doble served in the Marines, often wielding a hand-held grenade launcher on three-man patrols in and around the fire bases near the Laotian border.

Among the memories that haunted him, Doble said, is the time one Marine in his company threw rocks at the dead body of a Vietnamese soldier. "I should have said something," he said. "I should have stopped him."

Doble, 66, suppressed feelings of guilt and shame after being injured by mortar fire and returning home in 1969. He worked as a public school math teacher for three decades, and many colleagues had no inkling of his struggles. But gradually nightmares and visions of Vietnamese soldiers coming to kill him grew strong, and — at his wife's prompting — he sought treatment in recent years.

Often, he said, it was religious moments that brought out feelings of anguish, as when his church ­congregation applauded a speaker who, while serving in the military, had refused to launch a missile, or when his pastor prayed for peace at the time of Desert Storm, but not for the soldiers going into combat.

"For me, that was probably the worst part of it, since I joined the Marine Corps and made the choice to go to war," he said. "I just could not reconcile how I could ever be right with God again no matter what I did."

Part of confronting moral injury, Harris said, is persuading returning soldiers to let go of the guilt they have literally mounted on themselves during deployments as a defense mechanism against the terrors they face.

"They will convince themselves that a horrible situation was their fault. 'I didn't use my combat skills well enough and my buddy died,' " Harris said. "It gets them through that situation without feeling helpless. But the price when they get home — using a false sense of guilt to try and stay in control — that eats them alive."

Clinical trial

Healing that spiritual distress is the goal of an ongoing clinical trial at the Minneapolis VA involving 150 veterans with PTSD. Half are being placed in standard group therapy at area churches and community ­centers, and half are attending ­sessions with specific spiritual components.

An earlier pilot study by Harris found the spiritually based group therapy to be safe. Now the goal is to find out if the sessions that focus on spirituality cause greater reductions in guilt, shame and spiritual distress.

A religious conflict isn't necessarily at the root of moral injury, but it is a common one when considering that 90 percent of veterans believe in a higher power. Harris said her survey research from the National Guard showed moral injury among soldiers from different faiths, though she declined to identify whether it appeared more problematic among any particular religious or demographic group.

"I would not want that to be misinterpreted," she said.

Timm, the National Guard chaplain, said he will never forget the looks in the eyes of the two soldiers who had shot the unarmed driver in Iraq in 2006.

After using lethal force, some soldiers can't escape the belief that they have violated the commandment "thou shall not kill" even though scholars note the literal Hebrew translation is "thou shall not murder," and allows for the potential for lethal force in just circumstances.

In counseling these soldiers, Timm said, it was sometimes necessary to simply move past the question of whether the killing in combat was just. In the Christian tradition, he noted, God forgives those who ask for forgiveness.

"You guys have heard that before," he recalled telling the soldiers in Iraq. "but it's going to have to sink in at a whole new level, isn't it?"

Now, supervising the seven chaplains serving Minnesota Guard units, Timm said he has become more deliberate as he counsels soldiers preparing for deployments.

Military training by nature has a way of desensitizing troops to the use of lethal force almost of necessity. Trainers might use the term "kinetic military action" rather than terms such as killing or lethal force. This helps soldiers prepare for war, and the reflexive need to use lethal force to carry out missions and protect themselves. But sometimes ­soldiers overlook hard questions about whether their beliefs are consistent with those duties.

Advising a group of Minnesota Guard members before their 2012 deployment to a detention camp in Afghanistan, Timm asked the soldiers to contemplate what they would do if a prisoner tried to harm them, and how they would feel afterward.

"Whatever your faith tradition is," he remembered telling them, "you had better be able to handle the life and death stuff."

Clergy trained to gain trust

The Minnesota National Guard was a leader, nationally, with its Yellow Ribbon program to help soldiers return from deployments to their jobs, families and communities. That campaign also now trains local clergy on counseling returning soldiers and gaining their trust. Timm and Major Buddy Winn — a full-time support chaplain for the Minnesota Guard — trained a group of central Minnesota pastors at Camp Ripley in Little Falls last week.

Soldiers returning to Army bases have chaplains who have probably shared the combat experience, but Guard members returning to civilian settings might not seek help from pastors who haven't "been there," Winn said.

But with the Guard chaplains spread thin — Timm serves as pastor in a Lutheran church in Barron, Wis. — community religious leaders need to become more of a resource.

"Pain is pain," Winn said.

If moral injury can be measured and treated, Harris said, there are reasons for optimism. Soldiers with moral injuries who confront their religious beliefs and come to understand them often resolve their guilt and end up with stronger spirituality and faith.

"They're actually better and stronger at the end of it," she said.

Doble, the VA peer support volunteer, spent 30 years pushing aside the painful memories of Vietnam and ignoring the contradictions that emerged from his own religious beliefs. Having found stability in his life — and resolving the spiritual questions that had been punishing him — Doble said he wants to share the experience with other veterans.

"I was ashamed where there is no shame," he said, "and I want people to know that."

Jeremy Olson • 612-673-7744