Last week, General Martin Dempsey, chairman of the US Joint Chiefs of Staff, told a Congressional committee that his office was still considering whether or not the US should send ground troops to Iraq to fight ISIL (a.k.a. the Islamic State). Some in Congress and the military think the idea is past due, and that only American combat troops can neutralize the threat ISIL poses to Syria, Iraq, and beyond.

With Chuck Hagel’s resignation as defense secretary on Nov. 24—not to mention a move to slow the troop withdrawal in Afghanistan—a shift in policy may indeed be in the offing. But what everyone must understand is that if boots are put on the ground and a fighting war begins, American servicemen will not only likely be killed, but will also be killing.

That may sound obvious. Of course combat soldiers have to kill. And yet over the past year, as I’ve been reporting and writing about killing in combat—a project born from time spent covering the wars in Iraq, Afghanistan, and several other countries over the past decade—I’ve seen that this part of combat, obvious though it may be, remains one of the least discussed and most overlooked, despite the profound implications it has for all involved.

On some level, this is not surprising. Killing is a hard thing for civilians and leaders alike to address because it lays bare what war actually involves—something many would rather not know—and because it would make these wars far more disruptive, at least psychologically, than we were told they were supposed to be. Furthermore, many veterans themselves don’t know how or when to talk about it, particularly with people who have never fought. All they know is that they loathe the “hey-did-you-kill-anyone?” voyeurism they too often encounter.

Killing is a hard thing for civilians and leaders alike to address because it lays bare what war actually involves

All this means that troops must process the killing they’ve done on their own, often in isolation. Killing is still “the biggest moral decision” one can make and “the biggest moral taboo” one can break, Lt-Colonel Pete Kilner, who teaches a seminar at West Point called “The Morality of Killing,” told me. Yes, it’s part of the job soldiers signed up to do, but—as I heard from several veterans and military mental-health professionals—the military prepares recruits to kill far better than it prepares them to carry the confusion, rage, guilt, and doubt that can follow. In some ancient societies, said Bill Nash, a now-retired Navy psychiatrist I first met in Ramadi, civilians would greet returning soldiers and ritually wash their hands, cleansing them of the blood that their community asked them to spill, because it was their responsibility as well. In the US, Nash laments, the message has basically been, “You’re on your own with this.”

A burden for years to come

Not everyone is greatly affected by killing. Some may not give it another thought (which might be troubling in its own right). But the experiences of people I spoke to—people who knew what it was like to kill in firefights and in hand-to-hand combat, to kill many men while countering an ambush or to kill a child who’d picked up the gun of a fallen insurgent and pointed it at a group of Marines, or even to not kill the driver of a car bomb who then rammed a Humvee, killing everyone else inside it—showed that killing is something to be reckoned with not just in the moment, but for years to come.

Studies led by Dr. Shira Maguen of the San Francisco Veterans Affairs (VA) Center have shown that men who have killed in combat are more susceptible to post-traumatic stress disorder and other psychological injuries than those who have not. And one VA psychiatrist told me that she’d spoken to numerous vets for whom it had gotten it harder, not easier, to deal with as time passed, especially as they grew old enough to consider their own mortality. If a war fails to achieve its stated objectives—as Vietnam did—it can make the reasons for killing even harder to accept. Some recent vets of Iraq and Afghanistan, said the psychiatrist, are already asking, “What was it all for?”

This is not to cast troops who kill in combat as victims. They shouldcarry the weight of what they did. But they should not be forced to carry it alone. Their leadership, from the company level all the way to the Chief of Staff, is part of every killing that’s carried out. So too are the civilian architects of these wars. And the rest of us bear some responsibility as well. The killing a country does through its soldiers is part of its fabric and identity. The less it is examined, the less a country will know about itself, its impulses, and the impact of what it has trained and dispatched its sons and daughters to do.

A more honest conversation about what war is and what war does is a good place to start. Those now calling for boots on the ground in Iraq, Syria, or anywhere else, should be first to have it. They should understand and explain exactly what it will mean if troops are deployed, and they should press the military to give its charges tools that not only help them kill when they should, but also how to live with the killing they’ve done later in life. More counseling must be made available as well, as part of the broader overhaul of the VA, and steps taken to remove the stigma that still exists around seeking help for the psychological wounds of war. And no one should ask a veteran if he or she has killed anybody unless they really want to hear the answer—and are prepared to listen.