As readers of this website know, I have written a number of articles on war crimes and atrocities in response to the 1971 Senate testimony of John Kerry, who claimed that such acts were routinely committed by Americans in Vietnam with the knowledge of officers at all levels of command. I argued that while there were instances of Americans committing atrocities in Vietnam, they were no more widespread there than in earlier wars.

Despite my best efforts to avoid doing so, it seems I am destined to write once again on the issue of atrocities and war crimes. As the world knows by now, a Marine in Fallujah was captured on tape apparently shooting a wounded insurgent. Naturally, the tape has unleashed a furor and the incident is being investigated. The question is: Was this an unfortunate act of war, or was it a war crime? In my opinion, it was the former.

What are we talking about here? Let us be clear. Atrocities and war crimes are acts of violence in wartime whose brutality and cruelty exceed military necessity. They include, but are not limited to, looting, torture, rape, massacre, mutilation of the enemy dead, and the killing of captured soldiers or non-combatants. As I wrote earlier this year, the West has placed three constraints on its conduct of warfare: proportion, discrimination, and the positive law of war. Proportion means that particular actions must be proportionate to legitimate military necessity and not involve needless suffering or destruction. Discrimination means that direct, intentional attacks on noncombatants and non-military targets are prohibited.

The positive law of war derives from conventions, customs, the general principles of law, decisions in international law, and the writings of authorities. Standards regulating the conduct of war have followed two general paths: "Geneva law," protecting victims and innocents, and "Hague law," regulating land combat.

The most important conventions that underlie the positive law of war (and therefore provide guidelines for the conduct of war) include the Hague Convention IV of 1907, the Geneva Convention of 1949, the 1977 Protocols to those conventions, and the Nuremberg trials following World War II. Customs that constrain the conduct of war include military necessity, humanity, and chivalry.

The key to applying the law of war to particular situations is the principle of military necessity. This principle holds that, subject to the principles of humanity and chivalry, a belligerent is justified in applying the amount of force necessary to achieve the complete submission of the enemy as soon as possible, with the least expenditure of time, life, and resources. Military necessity recognizes that a commander’s overriding concern is the accomplishment of his mission and the safety of his troops. One would not attack a populated area, increasing the risks of civilian deaths, unless such an attack were essential to the campaign.

Humanity is the self-evident recognition of the fact that one’s enemy is also a human being. Prohibitions against killing or torturing prisoners, and the generally recognized obligation to provide medical treatment to wounded prisoners, flow from this principle.

Chivalry is the customary recognition of the idea that the strong protect the weak. Soldiers do not declare war on women or children because it is dishonorable to do so. If women or children engage in war, however, the principle of military necessity usually takes precedence over chivalry.

The dilemma, of course, is how to judge an action, given the likely clash among the main conditions. Do all conditions have to be met? Must all be met equally, or do some conditions take priority over others? The general conclusion is that all conditions must be met. But there is also the necessity of prudence in evaluating actions in war. Different times and circumstances may make one condition more important than another. Moreover, a reasonable judgment that a condition was met in a particular situation can be changed as a result of additional experience, information, or insight.

These principles lead us to the conclusion that we need to make a distinction in the case of the Marine in Fallujah. Clearly, a soldier who executes a prisoner, either on his own or under orders, has acted in cold blood and consequently has committed a war crime. Proportionality, humanity, and chivalry guide this judgment. But it seems to me that in the case of the Marine in question, military necessity trumped the other two conditions. He did not kill in cold blood, but responded to threatened danger in an uncertain environment. To fully convey this environment, let me reprint an e-mail from another Marine in Fallujah that I recently posted on The Corner at National Review Online:

This is one story of many that people normally don’t hear, and one that everyone does.

This is just one most don’t hear:

A young Marine and his cover man cautiously enter a room just recently filled with insurgents armed with AK-47s and RPGs. There are three dead, another wailing in pain. The insurgent can be heard saying, "Mister, mister! Diktoor, diktoor (doctor)!" He is badly wounded, lying in a pool of his own blood. The Marine and his cover man slowly walk toward the injured man, scanning to make sure no enemies come from behind. In a split second, the pressure in the room greatly exceeds that of the outside, and the concussion seems to be felt before the blast is heard. Marines outside rush to the room, and look in horror as the dust gradually settles. The result is a room filled with the barely recognizable remains of the deceased, caused by an insurgent setting off several pounds of explosives.

The Marines’ remains are gathered by teary-eyed comrades, brothers in arms, and shipped home in a box. The families can only mourn over a casket and a picture of their loved one, a life cut short by someone who hid behind a white flag. But no one hears these stories, except those who have lived to carry remains of a friend, and the families who loved the dead. No one hears this, so no one cares.

This is the story everyone hears:

A young Marine and his fire team cautiously enter a room just recently filled with insurgents armed with AK-47s and RPGs. There are three dead, another wailing in pain. The insurgent can be heard saying, "Mister, mister! Diktoor, diktoor (doctor)!" He is badly wounded. Suddenly, he pulls from under his bloody clothes a grenade, without the pin. The explosion rocks the room, killing one Marine, wounding the others. The young Marine catches shrapnel in the face.

The next day, same Marine, same type of situation, a different story. The young Marine and his cover man enter a room with two wounded insurgents. One lies on the floor in puddle of blood, another against the wall. A reporter and his camera survey the wreckage inside, and in the background can be heard the voice of a Marine, "He’s moving, he’s moving!"

The pop of a rifle is heard, and the insurgent against the wall is now dead.

Minutes, hours later, the scene is aired on national television, and the Marine is being held for committing a war crime. Unlawful killing.

And now, another Marine has the possibility of being burned at the stake for protecting the life of his brethren. His family now wrings their hands in grief, tears streaming down their face. Brother, should I have been in your boots, I too would have done the same.

For those of you who don’t know, we Marines, Band of Brothers, Jarheads, Leathernecks, etc., do not fight because we think it is right, or think it is wrong. We are here for the man to our left, and the man to our right. We choose to give our lives so that the man or woman next to us can go home and see their husbands, wives, children, friends and families.

For those of you who sit on your couches in front of your television, and choose to condemn this man’s actions, I have but one thing to say to you. Get out of you recliner, lace up my boots, pick up a rifle, leave your family behind, and join me. See what I’ve seen, walk where I have walked. To those of you who support us, my sincerest gratitude. You keep us alive.

I am a Marine currently doing his second tour in Iraq. These are my opinions and mine alone. They do not represent those of the Marine Corps or of the U.S. military, or any other.