Since the two recent NATO-led military strikes that accidentally killed dozens of Afghan civilians, I have been thinking a great deal about the psychic toll that killing takes on soldiers.

In 2007, I was an Army lieutenant leading a group on a house-clearing mission in Baquba, Iraq, when I called in an artillery strike on a house. The strike destroyed the house and killed everyone inside. I thought we had struck enemy fighters, but I was wrong. A father, mother and their children had been huddled inside.

The feelings of disbelief that initially filled me quickly transformed into feelings of rage and self-loathing. The following weeks, months and years would prove that my life was forever changed.

In fact, it's been nearly three years, and I still cannot remove from my mind the image of that family gathered together in the final moments of their lives. I can't shake it. It simply lingers.

I know that many soldiers struggle long after they leave the battlefield to cope with civilian deaths. It does not matter whether they were responsible for those deaths, whether it was a mistake of the command, of the weaponry, or even the fault of the enemy, who in parts of both Iraq and Afghanistan have been known to intentionally place or involve civilians, even children, in their operations. Just seeing the lifeless body of a little boy or girl is all it takes.

For many soldiers, what follows a killing is a struggle of the mind. We become aware that what we've seen has changed us. We can't unlearn it, and we continue to think of those innocent children. It is not possible to forget.

Killing enemy combatants comes with its own emotional costs. On the surface, we feel as soldiers that killing the enemy should not affect us — it is our job, after all. But it is still killing, and on a subconscious level, it changes you. You've killed. You've taken life. What I found, though, is that you feel the shock and weight of it only when you kill an enemy for the first time, when you move from zero to one. Once you've crossed that line, there is little difference in killing 10 or 20 or 30 more after that.

War erodes one's regard for human life. Soldiers cause or witness so many deaths and disappearances that it becomes routine. It becomes an accepted part of existence. After a while, you can begin to lose regard for your own life as well. So many around you have already died, why should it matter if you go next? This is why so many soldiers self-destruct when they return from a deployment.

I know something about this. The deaths that I caused also killed any regard I had for my own life. I felt that I did not deserve something that I had taken from them. I fell into a downward spiral, doubting if I even deserved to be alive. The value, or regard, I once had for my own life dissipated.

Five weeks ago, my first child, a son, was born. Not surprisingly, my thoughts often race back to the children I killed. With the birth of my son, I received the same gift I destroyed.

The fact that soldiers are trained and expected to kill as part of their job is something that few people wish to talk about. Many men and women coming back from war don't risk telling the stories that have so profoundly changed their lives.

In recent months I've been trying to honor the lives I took by writing and speaking in public about my experience, to show that those deaths are not tucked neatly away in a foreign land. They may seem distant, but they are not. Soldiers bring the ghosts home with them, and it's everyone else's job to hear about them, no matter how painful it may be.

Shannon P. Meehan is the author of "Beyond Duty." This article can also be found online at www.nytimes.com/opinion, as part of the blog Home Fires, which chronicles the experiences of soldiers returning from war.