One of many unforgettable moments in Philip Gourevitch’s book about the 1994 Rwanda genocide We Wish to Inform You that Tomorrow We Will Be Killed with Our Families is the author’s visit to Gitarama prison a year after the massacre. He finds a scene of incredible physical misery, though the sufferers barely complain. It’s the suspected Hutu perpetrators of the previous year’s genocide, not the Tutsi victims, who are crowded together here.

On the day of my visit to Gitarama Prison, six thousand four hundred and twenty-four prisoners formed a solid-looking knot, and I had to plan each step I took with care. It was difficult to figure out how the people fitted together — which limbs went with which body, or why a head appeared to have grown three legs without a torso in between. Many of the feet were badly swollen. The bodies were clad in rags.

Gourevitch is perplexed by what he finds as he visits various prisons holding thousands and thousands of suspected Hutu killers. The prisoners could easily escape, the author observes, but they don’t try. They just sit there.

Although the tightly packed inmates were all accused of terrible violence, they were generally calm and orderly; fights among them were said to be rare, and killings unheard of. They greeted visitors amiably, often with smiles and with hands extended for a shake … The captain kept calling out, “Here’s a journalist from the United States,” and the huddled men, squatting at our feet, clapped mechanically and made little bowing motions. It occurred to me that this was the famous mob mentality of blind obedience to authority which was often described in attempts to explain the genocide.

Blind obedience to authority is what these bewildered prisoners are guilty of, and it appears possible that they are so passive because they have already judged themselves to be guilty, that they look so confused because they don’t understand themselves how they suddenly transformed into murderers. Some of them admit this to Gourevitch, and later he talks to a former Hutu leader who has returned to the village where he presided over the murder of approximately seventy of his neighbors to ask for forgiveness from the few survivors who remain.

This man’s neighbors are not impressed and do not forgive him. Later, the man explains to Gourevitch that he felt helpless in April 1994, that he believed at the time that he had to either kill or be killed. When even the leaders feel helpless, how do we locate the source of guilt after a genocide occurs?

There is some sense of satisfaction in punishing individuals who directed or participated in acts of genocide, but the judgement of guilt feels like a category mistake, since an individual person can’t be guilty of genocide. An entire society must work together to carry out mass murder. Even a powerful politician or tyrant or general cannot successfully orchestrate a genocide without the voluntary support of an entire society. If a society must think together and act together to cause a genocide to occur, then the question of why genocides occur is a question of sociology rather than of individual psychology.

And yet when we try to analyze the cause of genocide, we always speak at the level of personal motivation, and we always describe the motivation in emotional or psychological terms. Hutus killed Tutsis because they hated them. Germans killed Jews because they were envious of their money. 19th century Americans killed Native Americans because they were greedy for their land. Soviet Russia starved Ukranians to death because Russians had a deep connection to Ukranian land. Islamic fundamentalists attack the USA because they hate our freedom.

These emotional or psychological explanations are probably a dead end. The explanations may be true in themselves, but a careful study of the actual genocides that took place all over the world in the last hundred years show that emotion and psychology don’t cause genocide at all. Neither do racial prejudice or religious belief or political ideology. No genocide in history has ever taken place because one group of people didn’t like another.

Other than susceptibility to obedience, or excessive willingness to conform to group action, personal characteristics or feelings of people who participate in a genocide are irrelevant to the cause of that genocide. When individuals participate in a group atrocity, they are not making decisions based on their personal feelings or opinions. They are acting as a group, and groups make decisions with a different kind of calculus.

Hutus might not have hated Tutsis. Germans might not have been envious of Jews. 19th century Americans might not have been greedy for land. Russians might not have had a deep connection to Ukranian lands. Islamic terrorists might not have cared whether Americans were free or not. These presumed motivations are all romanticized interpretations, created and popularized by amateur and professional historians after the fact to explain atrocities that previously took place.

What actually took place during each of these atrocities is more basic, more primitive. The word that will explain it has only three letters: war. Nearly every genocide or atrocity or massacre around the world in the last hundred years occurred in the context of war, and was a planned act of military strategy.

Once we begin to look at it this way, answers start to fall into place. Why do genocides occur? Let’s say we examine five representative cases:

• Rwanda in 1994
• The Chinese famine of 1958-1961 (Mao’s “Great Leap Forward”)
• The Holocaust
• The Holodomor (Stalin’s manufactured famine in Ukraine)
• The Armenian Genocide of 1915

Once you take the time to study these five case studies (or any others, from Srebenica to Bulgaria to Kampuchea to Darfur to Syria), a stunningly clear pattern emerges. Here are the steps that always fall into place before a genocide occurs.

1. Before a genocide occurs, there must be a state of total war and a perceived threat of annihilation in case the war is lost. This was true in all five cases above. The genocide in Rwanda took place in the midst of civil war, as a newly powerful Tutsi army stood poised at the country’s borders, about to invade. China was on permanent war footing and believed itself to be under threat of invasion on many fronts from Korea to Vietnam to Taiwan in 1958. Nazi Germany had committed to a fight to the death against England and Soviet Russia when it began slaughtering the Jews. Ten years earlier, Moscow suspected Ukraine of fostering a revolutionary independence movement that would resurrect the Russian Civil War. Turkey was in a fight to the death with Imperial Russia (there seemed to be a lot of that going around) when it ordered the death march of its Armenian population.

2. Most of these genocides were committed by the sides that were losing the war. This is an important truth: winners don’t commit genocide. Losers do. Genocide is usually an act of military desperation.

It’s a sad truth that, all too often, this act of military desperation turns out to be successful. For instance, Ukraine would remain under Russia’s oppressive rule for six more decades after the Holodomor. The independence movement that Stalin endeavored to wipe out was indeed wiped out for generations. Even today, Ukraine is struggling to emerge from under Russia’s thumb.

Thankfully, more often genocide does not succeed as a chess move. It may be too psychologically explosive, too demoralizing. In Rwanda, as Philip Gourevitch’s book describes, the obedient Hutus who slaughtered their neighbors seemed to lose their nerve halfway through the genocide. After expending so much effort and misery to kill 800,000 Hutsis, the Hutu Power movement suddenly collapsed against the advance of the invading Tutsi army. Philip Gourevitch speculates that individual Hutus were shocked and demoralized by their own descent into genocidal murder, and lost their will to fight. You can see some of this bewilderment and despair in the faces of the Gitarama prisoners at the top of this page.

3. In every genocide, the chosen victims are alien internal populations who are suspected of secret or open loyalty to the invading enemies. This is another essential component, though it is often not well understood. We all know that Turks murdered Armenians, but how many people know that this was considered an act of military necessity as Turkey fought Russia in World War I?

When these three conditions are present, genocide is likely to occur. It may or may not actually occur and this is where the emotional or psychological or spiritual characteristics of the individual people who constitute each society makes an important difference. It’s at this level that individual guilt is relevant whenever a genocide occurs: if the people refuse to conform to the military directive of their own government, the genocide cannot occur. The well-known story of Denmark’s refusal to participate in the Holocaust, even under Nazi occupation, is an example of this. The happily peaceful end of apartheid in South Africa, after the white government came to the conclusion that it must allow itself to dissolve, may be another:

Still, there appears to be a limit to the meaning of individual responsibility once a society finds itself in a state of total war. The most we can do is resist. The evidence seems to show that the overwhelming motivation for any genocide is simple military strategy. The strategic rationale for genocide is never based on emotion — not prejudice, not hatred, not sexual aggression, not personal greed, not religious belief — but is rather always based on the cold calculus of total war.

This seems to be an important conclusion, and I hope it’s a worthwhile culmination of the inquiry I’ve been running on this blog for the past few weeks. I’d like to know if you find this conclusion persuasive, and if you find it important, and if you find it surprising.

I find the conclusion surprising myself, and I think the discovery that genocide is always a consequence of rational military strategy rather than an expression of irrational personal psychology leads to an important question that I’d like to consider next weekend: doesn’t this conclusion amount to a very powerful indictment of militarism itself?