“The Operational Net Assessment was a tool that was supposed to allow us to see all, know all,” Major General Dean Cash, one of the senior JFCOM officials involved in the war game, admitted afterward. “Well, obviously it failed.”

On West Harrison Street in Chicago, two miles west of the city’s downtown, there is an ornate, block-long building designed and built in the early part of the last century. For the better part of one hundred years, this was the home of Cook County Hospital. It was here that the world’s first blood bank opened, where cobalt-beam therapy was pioneered, where surgeons once reattached four severed fingers, and where the trauma center was so famous—and so busy treating the gunshot wounds and injuries of the surrounding gangs—that it inspired the television series ER. In the late 1990s, however, Cook County Hospital started a project that may one day earn the hospital as much acclaim as any of those earlier accomplishments. Cook County changed the way its physicians diagnose patients coming to the ER complaining of chest pain, and how and why they did that offers another way of understanding Paul Van Riper’s unexpected triumph in Millennium Challenge.

Cook County’s big experiment began in 1996, a year after a remarkable man named Brendan Reilly came to Chicago to become chairman of the hospital’s Department of Medicine. The institution that Reilly inherited was a mess. As the city’s principal public hospital, Cook County was the place of last resort for the hundreds of thousands of Chicagoans without health insurance. Resources were stretched to the limit. The hospital’s cavernous wards were built for another century. There were no private rooms, and patients were separated by flimsy plywood dividers. There was no cafeteria or private telephone—just a payphone for everyone at the end of the hall. In one possibly apocryphal story, doctors once trained a homeless man to do routine lab tests because there was no one else available.

“In the old days,” says one physician at the hospital, “if you wanted to examine a patient in the middle of the night, there was only one light switch, so if you turned on the light, the whole ward lit up. It wasn’t until the mid-seventies that they got individual bed lights. Because it wasn’t air-conditioned, they had these big fans, and you can imagine the racket they made. There would be all kinds of police around because Cook County was where they brought patients from the jails, so you’d see prisoners shackled to the beds. The patients would bring in TVs and radios, and they would be blaring, and people would sit out in the hallways like they were sitting on a porch on a summer evening. There was only one bathroom for these hallways filled with patients, so people would be walking up and down, dragging their IVs. Then there were the nurses’ bells that you buzzed to get a nurse. But of course there weren’t enough nurses, so the bells would constantly be going, ringing and ringing. Try listening to someone’s heart or lungs in that setting. It was a crazy place.”

Reilly had begun his medical career at the medical center at Dartmouth College, a beautiful, prosperous state-of-the-art hospital nestled in the breezy, rolling hills of New Hampshire. West Harrison Street was another world. “The first summer I was here was the summer of ninety-five, when Chicago had a heat wave that killed hundreds of people, and of course the hospital wasn’t air-conditioned,” Reilly remembers. “The heat index inside the hospital was a hundred and twenty. We had patients—sick patients—trying to live in that environment. One of the first things I did was grab one of the administrators and just walk her down the hall and have her stand in the middle of one of the wards. She lasted about eight seconds.”

The list of problems Reilly faced was endless. But the Emergency Department (the ED) seemed to cry out for special attention. Because so few Cook County patients had health insurance, most of them entered the hospital through the Emergency Department, and the smart patients would come first thing in the morning and pack a lunch and a dinner. There were long lines down the hall. The rooms were jammed. A staggering 250,000 patients came through the ED every year.

“A lot of times,” says Reilly, “I’d have trouble even walking through the ED. It was one gurney on top of another. There was constant pressure about how to take care of these folks. The sick ones had to be admitted to the hospital, and that’s when it got interesting. It’s a system with constrained resources. How do you figure out who needs what? How do you figure out how to direct resources to those who need them the most?” A lot of those people were suffering from asthma, because Chicago has one of the worst asthma problems in the United States. So Reilly worked with his staff to develop specific protocols for efficiently treating asthma patients, and another set of programs for treating the homeless.

But from the beginning, the question of how to deal with heart attacks was front and center. A significant number of those people filing into the ED—on average, about thirty a day—were worried that they were having a heart attack. And those thirty used more than their share of beds and nurses and doctors and stayed around a lot longer than other patients. Chest-pain patients were resource-intensive. The treatment protocol was long and elaborate and—worst of all—maddeningly inconclusive.

A patient comes in clutching his chest. A nurse takes his blood pressure. A doctor puts a stethoscope on his chest and listens for the distinctive crinkling sound that will tell her whether the patient has fluid in his lungs—a sure sign that his heart is having trouble keeping up its pumping responsibilities. She asks him a series of questions: How long have you been experiencing chest pain? Where does it hurt? Are you in particular pain when you exercise? Have you had heart trouble before? What’s your cholesterol level? Do you use drugs? Do you have diabetes (which has a powerful association with heart disease)? Then a technician comes in, pushing a small device the size of a desktop computer printer on a trolley. She places small plastic stickers with hooks on them at precise locations on the patient’s arms and chest. An electrode is clipped to each sticker, which “reads” the electrical activity of his heart and prints out the pattern on a sheet of pink graph paper. This is the electrocardiogram. In theory, a healthy patient’s heart will produce a distinctive—and consistent—pattern on the page that looks like the profile of a mountain range. And if the patient is having heart trouble, the pattern will be distorted. Lines that usually go up may now be moving down. Lines that once were curved may now be flat or elongated or spiked, and if the patient is in the throes of a heart attack, the ECG readout is supposed to form two very particular and recognizable patterns. The key words, though, are “supposed to.” The ECG is far from perfect. Sometimes someone with an ECG that looks perfectly normal can be in serious trouble, and sometimes someone with an ECG that looks terrifying can be perfectly healthy. There are ways to tell with absolute certainty whether someone is having a heart attack, but those involve tests of particular enzymes that can take hours for results. And the doctor confronted in the emergency room with a patient in agony and another hundred patients in a line down the corridor doesn’t have hours. So when it comes to chest pain, doctors gather as much information as they can, and then they make an estimate.

The problem with that estimate, though, is that it isn’t very accurate. One of the things Reilly did early in his campaign at Cook, for instance, was to put together twenty perfectly typical case histories of people with chest pain and give the histories to a group of doctors—cardiologists, internists, emergency room docs, and medical residents—people, in other words, who had lots of experience making estimates about chest pain. The point was to see how much agreement there was about who among the twenty cases was actually having a heart attack. What Reilly found was that there really wasn’t any agreement at all. The answers were all over the map. The same patient might be sent home by one doctor and checked into intensive care by another. “We asked the doctors to estimate on a scale of zero to one hundred the probability that each patient was having an acute myocardial infarction [heart attack] and the odds that each patient would have a major life-threatening complication in the next three days,” Reilly says. “In each case, the answers we got pretty much ranged from zero to one hundred. It was extraordinary.”