In late 2005, the 1st Battalion of the 101st Airborne Division's fabled 502nd Infantry Regiment deployed to a 330 sq. mi. ribbon of land south of Baghdad that was dubbed the "Triangle of Death." Underequipped and undermanned, the 1-502nd arrived in perhaps the most dangerous part of Iraq at its most dangerous moment.

Suffering from a particularly heavy death toll, a leadership vacuum and rapidly declining morale and discipline, four soldiers from the 1-502nd's 1st Platoon, Bravo Company, would perpetrate one of the worst war crimes known to have been committed by U.S. forces during the Iraq war, or any war for that matter. On March 12, 2006, Specialist Paul Cortez, Specialist James Barker, Private First Class Jesse Spielman and Private First Class Steven Green raped 14-year-old Abeer Qassim Hamzah Rashid al-Janabi and murdered her, her parents and her 6-year-old sister.

The first experpt of TIME contributing editor Jim Frederick's new book, Black Hearts: One Platoon's Descent into Madness in Iraq's Triangle of Death, demonstrated Steven Green's downward psychological spiral. The second and final excerpt highlights how Green and his co-conspirators masterminded their crime ...

By the spring of 2006, the psychological isolation that 1st Platoon had been experiencing throughout the deployment was becoming nearly total. "First Platoon had become insane," declared platoon-member Sergeant John Diem flatly. "What does an infantry rifle platoon do? It destroys. That's what it's trained to do. Now turn that 90 degrees to the left, and let slip the leash, and it becomes something monstrous. It's not even aware of what it's doing."

Some of the mental states that the men described are well documented by psychologists studying the effect of combat on soldiers. The men talked about desensitization, how numbed they were to the violence. They passed around short, graphic, computer-video compilations of collected combat kills and corpses found in Iraq. Iraqis were not seen as humans. Many soldiers actively cultivated the dehumanization of locals as a secret to survival. "You can't think of these people as people," opined Sergeant Tony Yribe, another member of 1st Platoon. "If I see this old lady and say, 'Ah, she reminds me of grandmother,' but then she pulls out a f___ing bomb, I'm not going to react right." Children were considered insurgents or future insurgents, and women were little more than insurgent factories.

Specialist James Barker described the paradoxical yet typical swings combat-weary soldiers have between thinking they are doomed and thinking they are invincible. "I knew I was going to die, it was just a matter of time, so I just didn't care. I would run straight at somebody shooting at me instead of taking cover. That was my mentality: I'm already dead so, f___ it, what can anybody do to me? I'd gotten shot at so many times and blown up so many times, and hadn't taken a scratch that it's like, 'Oh, f___, I'm untouchable. I am a badass and nobody can f___ with me.' "

House searches turned extremely violent. Suspected insurgents were beaten as a matter of course, with the full blessings and, in fact, insistence of some team leaders and squad leaders. Sergeants would egg the younger soldiers on, making fun of privates who didn't hit detainees hard enough.

One of Bravo Company's primary tasks was to man traffic control points (TCPs) on one of the main roads in the area. This was a particularly loathed assignment, since the TCPs were remote and dangerously underfortified. At the beginning of March, Bravo Company's 1st Platoon began a rotation out at the TCPs that would ultimately last 21 days, two weeks longer than the usual rotation. Specialist Paul Cortez was put in charge of TCP2. The spiral of poor discipline, substance abuse, brutality and lack of senior oversight that began months ago was continuing unabated. By March 12, the small group of young soldiers Cortez was leading, including Steven Green, had reached their breaking point.

On March 12, Green was pulling predawn guard in the gun truck at TCP2. He'd been up for 18 hours. "I've had it," he thought to himself. This was it. Not long after, he was hanging out with Barker and Cortez in the courtyard area of the TCP.

"When I'm on guard next time," he told them, "I'm going to waste a bunch of dudes in a car. And we'll just say they were running the TCP."

"Don't do that!" Cortez exclaimed, "Don't do it while I'm here. I'm supposed to be running this s___. I don't want to get in trouble."

Barker agreed.

"I've got a better idea," he said. "We've all killed hadjis," Barker said, using an epithet common among soldiers for Iraqis, "but I've been here twice and I still never f___ed one of these bitches." Cortez's interest was piqued. They talked about it, the three of them, semiseriously but somewhat distractedly as they did other things throughout the rest of the morning. Sometimes Barker and Cortez would confer privately, sometimes Green and Barker would, and sometimes all three of them would talk.

Barker had already picked the target. There was a house, not far from here, that would be perfect. They had been on a patrol there just a little while ago. There was only one male and three females in the house during the daytime — a husband, a wife and two daughters. One was young, but the other was a teenager or in her twenties, it was hard to tell with all the clothes the women wore, as they frequently lamented. But Barker thought she was pretty hot, at least for a hadji chick. Barker told them that they should go over there right now.

Witnesses were a problem, however. They knew they couldn't leave anyone alive. Barker asked Green if he was willing to take care of that, even if there were some women involved. Barker knew Green was always begging to kill Iraqis, if only someone would say the word. "You'll kill them, right?" Barker asked.

Absolutely, Green replied. "It don't make any difference to me," Green said. "A hadji is a hadji."

Over several hours and several conferences, they went back and forth on whether to do it or not. Barker was pushing hard, and Green was game, but Cortez was waffling. Finally Cortez said, "No, f___ it, this is crazy. F___ this. There is no way we are doing this s___."

At around noon, with a new wave of boredom taking hold, the three of them, along with Private First Class Jesse Spielman, sat down outside with a cardboard box as a table to play some rounds of Uno. They drank Iraqi whiskey. Barker had bought five or six 12-oz. cans of the stuff from an Iraqi army soldier at the very reasonable price of $5 per can. There was some bottled whiskey on hand, too. They mixed the whiskey in an empty liter water bottle with some Rip-Its, a carbonated energy drink. Green liked his whiskey straight. Over several hands of cards, they got drunk as they talked about all the things they usually talked about. Girls, cars, music, sports, how much they hated this place, how much they hated hadj.

During most of the game, Private Bryan Howard had been on his cot, listening to his CD player in another room. Howard was just 18, a brand-new private who had arrived in November. Though he had only missed a little more than a month of the deployment, he was still considered a new guy. He was hazed often, and not included in a lot of things.

The men, as they played, got drunker and drunker. Cortez later rated their level of intoxication at 6 or 7 on a scale of 10. Barker said he felt about the equivalent of having 6 to 8 beers.

During one of the rounds, Cortez popped up and said, "F___ it, we are going to do this thing." He outlined the mission and he divvied up the duty assignments just like a legit patrol. He and Barker would take the girl, Green would kill the rest of the family, Spielman would pull guard and Howard would stay back and man the radio. He told everyone to grab their rifles and get ready to head out.

Spielman packed up the cards and put them away. Cortez went out to the truck to check on Private Seth Scheller, who was the only one on guard. Scheller was a brand-new private and he had been in the truck all morning.

Cortez returned and said, "If we are going to do this, let's go before I change my mind." He and Barker started changing their clothes, putting on their black, silk-weight Polartec tops and bottoms and balaclava thermal face masks to obscure their faces. They wanted to look like insurgents, they said, and ordered Spielman and Green to do the same. Green objected, saying he wasn't changing. At least take your patches off, Cortez said, which Green did. Spielman only wore his uniform bottoms and a T-shirt while Green kept his whole uniform on. Cortez insisted they cover their faces so Green tied a T-shirt around his head and Spielman put on a pair of sunglasses.

Green grabbed a shotgun, Cortez and Barker snagged M-4 rifles. Spielman picked up an M-14, a larger, heavier rifle than the M-4 frequently used as a longer-range weapon.

Cortez briefed Howard. Cortez told him they knew about an Iraqi girl who lived near here and they were going to go out and f___ her. To Howard, it was the most insane thing he'd ever heard. He did not believe them, but he also could not believe that they were actually leaving for somewhere, leaving him and Scheller alone. Cortez gave the radio and told him to call if there were any patrols or humvees coming through.

The men, armed and disguised, headed out the back of the TCP.