Most will return to the United States more or less intact. But some come home the hard way - on a stretcher, bloody and broken.
And, as Correspondent Bob Simon says, there are few bloodier or more broken than Chris Schneider.
Schneider says he believed in the war in Iraq, and liked wearing the uniform. "[I was] proud to wear it. I loved wearing it," says Schneider, a Kansas boy straight off the recruitment poster.
He went to college on a wrestling scholarship, started a family, and joined the Army Reserves. This past January, his unit was providing security for a supply convoy traveling through 100 miles of dangerous Iraqi desert. He was riding in a two-and-a-half ton cargo truck, armed to the teeth.
"In my vehicle there was my driver, there was my 50-cal gunner who was in a turret on top," says Schneider. "And then there was myself and another individual in back. We both had M249 machine guns."
Schneider saw another convoy coming in his direction - a line of HETS (heavy equipment transports), big rigs on steroids, hogging the road. The first HET just missed hitting his truck. The second one did not.
"It threw me up over my vehicle, over the HET and about 50 feet into the field on the left," says Schneider. "When I landed, the next HET in line had locked up their brakes to keep from rear ending the one that we hit. And when he came to rest, the first set of tires on his trailer were parked on my pelvis. And the second set had my lower leg wedged in it to the axle. I've been told a rough estimate of approximately 120,000 to 140,000 pounds."
Today, Schneider walks with a limp, on his artificial leg. But even though he was injured while on a mission in a war zone – and even though he'll receive the same benefits as a soldier who'd been shot - he is not included in the Pentagon's casualty count. Their official tally shows only deaths and wounded in action. It doesn't include "non-combat" injured, those whose injuries were not the result of enemy fire.
"It's a slap in the face. Although it was through no direct hostile action, I was on a mission that they'd given me in hostile territory. Hostile enough that we had to have a perimeter set up at the time of my accident to prevent from an ambush or an attack," says Schneider. "For those of us that were unfortunate enough to get injured. Whether it was hostile action or not, we're all paying the same price."
How many injured and ill soldiers, sailors, airmen and marines - like Chris Schneider - are left off the Pentagon's casualty count?
Would you believe 15,000? 60 Minutes asked the Department of Defense to grant us an interview. They declined. Instead, they sent a letter, which contains a figure not included in published casualty reports: "More than 15,000 troops with so-called 'non-battle' injuries and diseases have been evacuated from Iraq."
Many of those evacuated are brought to Landstuhl in Germany. Most cases are not life-threatening. In fact, some are not serious at all. But only 20 percent return to their units in Iraq. Among the 80 percent who don't return are GIs who suffered crushing bone fractures; scores of spinal injuries; heart problems by the hundreds; and a slew of psychiatric cases. None of these are included in the casualty count, leaving the true human cost of the war something of a mystery.
"It's difficult to estimate what the total number is," says John Pike, director of a research group called GlobalSecurity.org.
As a military analyst, Pike has spoken out against both Republican and Democratic administrations. He's weighed all the available casualty data and has made an informed estimate that goes well beyond what the Pentagon has released.
"You have to say that the total number of casualties due to wounds, injury, disease would have to be somewhere in the ballpark of over 20, maybe 30,000," says Pike.
His calculation, striking as it is, is based on the military's own definition of casualty – anyone "lost to the organization," in this case, for medical reasons. And Pike believes it's no accident that the military reports a number far lower than his estimate.
"The Pentagon, I think, is afraid that they're going to lose public support for this war, the way they lost public support for Vietnam back in the 1960s," says Pike. "And minimizing the apparent cost of the war, I think, is one way that they're hoping to sustain public support here at home."
60 Minutes asked the assistant secretary of Defense for Health Affairs about that claim - that casualties are being underreported, for political reasons. And we got a flat denial. In a letter, he told us, "We in the Department of Defense categorically reject the notion that we are underreporting casualties from Operation Iraqi Freedom."
He pointed out that he'd already provided us with some figures - the 15,000 evacuations of non-combat injured and ill. Still, Pike says the military is trying to minimize the casualty count. It's an effort Pike believes is misguided, because he says that even if Americans understood the full human cost of the war, public support would not weaken.
"I think that all of the public opinion polling that we're seeing suggests that the public is prepared to sustain far higher casualties than politicians give them credit for," says Pike. "I think that it's basically that the politicians and the Pentagon, don't have confidence in the American people."
The Department of Defense did not include non-battle injuries in its casualty reports in other recent wars, either. But that's of little comfort to Joel Gomez, who was riding in the back of a Bradley fighting vehicle, looking for insurgents, when disaster struck.
"Unfortunately, the Bradley was too heavy for the road, a dirt road, and the ground gave way. And we wound up flipping down the mountain. And it landed upside-down in the Tigris River," says Gomez.
His two buddies were killed. Gomez made it out, but he's now paralyzed. "[It's] a horrific change. I can't move my legs. I can't move my arms," says Gomez. "It just totally changes your life in a manner that you could never imagine."
Even though Gomez tumbled into the Tigris while looking for insurgents, he is, by the Pentagon's definition, "non-combat injured."
"They blow it off and say it's just an accident," say Gomez. "I'm sure that somebody getting shot in the back would just be an accident. But that's how they see it."
The Department of Defense says the injuries and illnesses suffered by Gomez and thousands of other troops should not be taken out of context. In their letter to 60 Minutes, they said: "In order to understand rates of injuries and diseases, it is necessary to understand what the normal or usual rates of injuries and diseases might be in other situations."
What does this mean? That there are always going to be a certain number of accidents and injuries, war or no war – though they offer no numbers for comparison.
"Soldiers and Marines are gonna get sick. They're gonna get into accidents. But there's gonna be more disease, more accidents, more psychiatric stress in Iraq than if they were back here," says Pike, who adds that hundreds of troops in Iraq have been so paralyzed by stress that they've had to be medically evacuated – though you won't see them reported in the casualty count.
Traditionally, that count has not included combat stress. It was long thought, in the military's macho culture, that psychological trauma is best suffered in silence.
Graham Alstrom has been back from Iraq for over a year, but he's still haunted by what he saw – and what he did to other people. "Some of them I shot. Some of them I blew up with grenades. Some of them were stabbed," says Alstrom.
The memories of killing invaded his mind. Soon after he returned home, Alstrom's life began to unravel.
"The drinking started immediately. I stopped sleeping. And I started getting very angry. I didn't want to talk to my family anymore. I didn't want them to see me. I didn't want to see them. I felt like they were ashamed of me," says Alstrom. "I was partly ashamed of some of the things I had done. …I couldn't separate the killing people and killing them in combat."
He says he's frustrated that the military says his illness is not combat-related. "I know what I was like before I went to combat. I had a life beyond the Army," says Alstrom. "I talked to my family. I'd share feelings and emotions with people I cared about. I lived a very regular life."
Alstrom won't get a Purple Heart for his service in Iraq. It was only his mind that was wounded in battle. "It doesn't matter what the paperwork says. We know what happened over there. We know what we did over there," says Alstrom. "And no piece of paperwork saying that I'm not a casualty could ever take that away. For any of us."
They've had so much taken away already, but both Alstrom and Schneider insist that what remains inside them is the heart of a good soldier.
"I'm very supportive of why we're there. I'm very supportive of what we did while I was there," says Schneider. "I believe wholeheartedly that not only should we have gone, but that we've done the right thing."
Now, he'd like the military to do the right thing, too.
"Every one of us went over there with the knowledge that we could die," says Schneider. "And then they tell you - you're wounded - or your sacrifice doesn't deserve to be recognized, or we don't deserve to be on their list – it's not right. It's almost disgraceful."