Even before the Congressional hearings on the criminal abuse of Iraqi detainees at Abu Ghraib prison, Colin Powell brought up My Lai, the Vietnamese village where, in 1968, American troops slaughtered more than 400 civilians, mostly old people, women and children. He cited it as the kind of thing that can happen in wars. I also thought of My Lai, but for somewhat different reasons.

Both Abu Ghraib and My Lai are examples of what I call an "atrocity-producing situation"--one so structured, psychologically and militarily, that ordinary people, men or women no better or worse than you or I, can regularly commit atrocities. In Vietnam that structure included "free-fire zones" (areas in which soldiers were encouraged to fire at virtually anyone); "body counts" (with a breakdown in the distinction between combatants and civilians, and competition among commanders for the best statistics); and the emotional state of US soldiers as they struggled with angry grief over buddies killed by invisible adversaries and with a desperate need to identify some "enemy."

The Iraq military environment is quite different from that of Vietnam, but there are some striking parallels. Iraq is also a counterinsurgency war in which US soldiers, despite their extraordinary firepower, feel extremely vulnerable in a hostile environment, and in which higher-ranking officers and war planners feel frustrated by the great difficulty of tracking down or even recognizing the enemy. The exaggerated focus on interrogation, including the humiliation of detainees as a "softening-up" process, reflects that frustration.

We can thus speak of a three-tier dynamic. Foot soldiers--in this case MPs and civilian contractors--do the dirty work, as either orchestrated or at least sanctioned by military intelligence officers in charge of interrogation procedures. The latter in turn act on pressure from higher-ups to extract information that will identify "insurgents" and possibly lead to hidden weapons.

What ultimately drives the dynamic is an ideological vision that equates Iraqi fighters with "terrorists" and seeks to further justify the invasion. All this is part of the amorphous, even apocalyptic, "war on terrorism," as is the practice of denying the human rights of detainees labeled as terrorists, a further stimulus for abuse. Grotesque improvisations can occur at different levels--whether in the form of interrogators' ideas about inflicting sexual humiliation or in foot soldiers' methods of carrying out those instructions or responding to more indirect messages from above.

Recognizing that atrocity is a group activity, one must ask how individual soldiers can so readily join in. I believe they undergo a type of dissociation I call "doubling"--the formation of a second self. Nazi doctors could continue to be ordinary husbands and fathers when on leave from their murderous work in Auschwitz. Similarly, Tony Soprano is a likable fellow who cares about his children but is in the business of maiming and killing. The individual psyche can adapt to an atrocity-producing environment by means of a subself that behaves as if autonomous and thereby joins in activities that would otherwise seem repugnant. Ironically and sadly, this is an expression of the same genius for adaptation that has so well served Homo sapiens in the evolutionary process.

In environments where sanctioned brutality becomes the norm, sadistic impulses, dormant in all of us, are likely to be expressed. The group's violent energy becomes such that an individual soldier who questions it could be turned upon. (A Vietnam veteran who had been at My Lai told me he had felt himself in some danger when he not only refused to fire but pointedly lowered the barrel of his gun to the ground.) To resist such intense group pressure, an unusual combination of conscience and courage is required.

This kind of atrocity-producing situation can exist, with most of the characteristics I have described, in ordinary civilian prisons. And it surely occurs in some degree in all wars, including World War II, our last "good war." But a counterinsurgency war in a hostile setting, especially when driven by profound ideological distortions, is particularly prone to sustained atrocity--all the more so when it becomes an occupation.

To attribute the scandal at Abu Ghraib to "a few bad apples" or to "individual failures" is poor psychology and self-serving pseudomorality. To be sure, individual soldiers and civilians who participated in it are accountable for their behavior, even under such pressured conditions. But the greater responsibility lies with those who planned and executed the war on Iraq and the "war on terrorism" of which it is a part, and who created, in policy and attitude, the accompanying denial of rights of captives and suspects.

Psychologically and ethically, responsibility for the crimes at Abu Ghraib extends to the Defense Secretary, the Attorney General and the White House. Those crimes are a direct expression of the kind of war we are waging in Iraq.

• Get The Nation at home (and online!) for 75 cents a week!
• If you like this article, consider making a donation to The Nation.