The U.S. military, it occurred to me as I watched it in action, is one of the biggest habit-formation experiments in history. Basic training teaches soldiers carefully designed habits for how to shoot, think, and communicate under ﬁre. On the battleﬁeld, every command that’s issued draws on behaviors practiced to the point of automation.





The entire organization relies on endlessly rehearsed routines for building bases, setting strategic priorities, and deciding how to respond to attacks. In those early days of the war, when the insurgency was spreading and death tolls were mounting, commanders were looking for habits they could instill among soldiers and Iraqis that might create a durable peace.

I had been in Iraq for about two months when I heard about an ofﬁcer conducting an impromptu habit modiﬁcation program in Kufa, a small city ninety miles south of the capital. He was an army major who had analyzed videotapes of recent riots and had identiﬁed a pattern: Violence was usually preceded by a crowd of Iraqis gathering in a plaza or other open space and, over the course of several hours, growing in size. Food vendors would show up, as well as spectators. Then, someone would throw a rock or a bottle and all hell would break loose.

When the major met with Kufa’s mayor, he made an odd request: Could they keep food vendors out of the plazas? Sure, the mayor said. A few weeks later, a small crowd gathered near the Masjid al-Kufa, or Great Mosque of Kufa. Throughout the afternoon, it grew in size. Some people started chanting angry slogans. Iraqi police, sensing trouble, radioed the base and asked U.S. troops to stand by. At dusk, the crowd started getting restless and hungry. People looked for the kebab sellers normally ﬁlling the plaza, but there were none to be found. The spectators left. The chanters became dispirited. By 8 p.m., everyone was gone.

When I visited the base near Kufa, I talked to the major. You wouldn’t necessarily think about a crowd’s dynamics in terms of habits, he told me. But he had spent his entire career getting drilled in the psychology of habit formation.