Recently, I watched the Dutch documentary “First Kill” about the experiences of veterans and reporters during the Vietnam War. The film delves into the complex psychology of killing and the American military’s obsession with “body count” during the war. In a war where territory acquisition was difficult, the military measured its success by the number of enemies its soldiers killed.

As Nick Turse so compellingly argues in his book “Kill Anything That Moves,” the body count obsession led to the killing of countless non-combatants, including the elderly, women, and children. Each corpse was added to a unit’s tally and military leaders rarely investigated whether the corpses were actually those of Viet Cong.

What caused so many young American men to act so viciously in Vietnam? While Turse blames the military’s efforts to dehumanize Vietnamese (for instance, using racial slurs), the documentary “First Kill” suggests that the answer has more to do with crossing a moral line. After being told your whole life that murder is wrong, soldiers were put in a situation where they were expected to not only kill, but kill lots of people. Under those conditions, murder becomes normal.

As veteran Billy Heflin in “First Kill” recalls,

When I was in America I was called a baby killer, because we killed kids. It was easy to pull the trigger. Just another trigger out there. It was the enemy. They had to be killed. You didn’t think about. You didn’t say, man, I killed a little kid. You didn’t think about that.

Later in the film, Billy talks about how difficult it was for him to come back to the United States after being trained as a killer. He says he misses killing and the good feeling that came from shooting the enemy.

How does one go back to a society where killing is immoral after being told by your government to kill? Certainly, some veterans have an easier time at it than others. But for vets like Billy, it is something that they will struggle with for a long time.

For Vietnam veterans suffering from “soldier’s heart,” I recommend checking out psychotherapist Ed Tick. He and his wife lead healing journeys back to Vietnam each year with a focus on forgiveness and reconciliation.