It is 95 degrees at Georgia's Fort Benning, and most of the guys have been in the Army for three days.
Looking at their faces, you can see the term "men" doesn't quite apply. Many of them were driven to this boot camp by their moms.
"She had to leave early because she couldn't stop crying. It was kind of emotional," Pvt. Aaron Perry said.
Amid the sweat and chaos of their first days, they get to place one two-minute phone call.
Sometimes it helps the homesickness, but often it only makes it worse.
"I called my parents. Neither one of my parents wanted me to join," Pvt. Keith Cassan said. "When I tried to call home yesterday, nobody answered the phone and I had to leave a message."
"I was upset and I wanted to talk to them," he said.
If these men weren't here, they might be playing soldier with a video-game joystick.
Here, however, they hold real guns and scream battle cries -- "Ho ha, I want to kill somebody" -- that would have gotten them in trouble just weeks before.
Do they really want to kill somebody?
"Right now, no sir," Pvt. Kevin Pawaski said. "I'm just getting my training ready to prepare me."
Pvt. Stan Brassley, however, says he is looking forward to shooting in Iraq.
"I just wanted to go to Iraq," he said. "I wanted to be able to shoot my rifle. It'll be intense, but it'll be fun."
During World War II, an Army historian followed infantrymen into combat, interviewed hundreds more, and discovered that in their first battle, 75 percent of young soldiers didn't shoot back.
How do you get them to overcome fear in the face of intense fire?
"I think what you do is you don't deny it," Lt. Col. Randall White said. "I mean you don't say, 'Look man, you're not going to be afraid!' You tell them, 'Hey, look that's natural. This is not a natural vocation.'"
It isn't natural to kill another human, even in war.
So today, the Army spends $2 billion a year changing that instinct, molding boys into weapons.
They start by stripping away their identity.
The Army's team of 117 behavioral psychologists believe that a private may love his country, but that he's more likely to kill for his unit.
They spend the first three weeks at boot camp in what is called "total control."
By eating and dressing and suffering exactly like his so-called "battle buddy," a private learns mutual pain and joint pleasure. Over time, there comes an overwhelming sense of obligation to defend that buddy's life.
"Well, they say it's about probably two out of this entire company that will be killed within the next year," Pvt. Albert Brady said. "Those are the chances right now."
They are also shown movie clips in their instruction: "Braveheart" for courage and "Rudy" for teamwork.
One in 10 privates don't make it through the 14-week boot camp.
Those who complete the session make an all-night march, carrying 60-pound packs. They are led to a bonfire to toast to the grim missions of soldiers past and to their future.
On graduation day, the mothers who said goodbye 14 weeks earlier marvel at the change.
It is a day tinged with equal parts pride and fear.
"I'd be lying if I said I wasn't a little scared," one mother said.
Unless things change, many of these soldiers will be in Iraq within months. Unlike those in previous wars, however, every infantryman is likely to shoot back.