[The Reaper]

He didn't specify his salary, but Americans and other Westerners in the business tend to make between $400 and $700 a day, sometimes a good deal more. (The non-Westerners earn far less. Triple Canopy's Fijians and Chileans make between $40 and $150 dollars each week and sleep in crowded barracks at the Baghdad base, while the Americans sleep in their own dorm rooms. The company explained the difference in salaries in terms of the Americans' far superior military backgrounds and their higher-risk assignments.) Americans with Triple Canopy stay in Iraq for three-month rotations, working straight through. Then they're sent on leave for a month, returning if they wish. Depending on how much time they spend in the States over the course of a year, most of their income can be tax-free.

Yet it wasn't all about the pay, not for everyone. ''The money, sure,'' Al, a Triple Canopy manager in Baghdad, said. Like plenty of others with the company, he was middle-aged and had retired from the rarefied world of Delta. ''But it's the excitement, the camaraderie.''

And back in the Chicago suburb where I visited the company in May, in its new, sprawling offices (which Triple Canopy would soon be exchanging for a similar setup outside Washington, in order to be closer to its main source of income, the U.S. government), I heard Matt Mann talk exuberantly about ''creating a national asset.'' It would have been easy to be exuberant merely because of the profits he was taking in; it would have been easy to be downright giddy.

But his enthusiasm seemed to come, as well, from other things. He spoke about the waste of Special Operations stars, ''men whose intelligence is equal to the best attorneys, the best doctors,'' men who had survived the harshest training, who had learned to operate on their own in alien cultures, who ''don't know how to fail.'' Their talents, he said, were going unrecognized and unused when they left the military and entered civilian society. A long window beside him looked out on a perfectly manicured office park, its pond rippling delicately. Wearing jeans and a short-sleeved sport shirt with a summery print, he leaned back behind his blond wood desk, hands behind his head, strong, tanned arms on display. In a sense, he might have been any renegade businessman who had conjured a new product and found himself in a spot of corporate comfort. But a map of Iraq, its yellow tones in quiet contrast to the blond of the wood, was posted on the wall. He didn't care to talk about his personal thoughts on the war but saw himself as creating a collection of talent that was driven less by the '' 'me' mind frame,'' he said, than by patriotism.

In an office near Mann's sat Al Buford, the company's manager of recruiting, wearing sharply pressed khakis and a pale blue dress shirt. On a bookshelf behind him, a framed photograph showed him in jungle camouflage, on an Army Special Operations mission in Panama. Facing him on his desk, his computer was loaded with scores from the psychometric exam Triple Canopy gives its potential employees. The company's three-week training and selection course includes multiple-choice word analogy and number pattern questions between the high-speed driving drills and target tests at the firing range. And there are hundreds of questions designed to catch personality problems before the company gives a candidate a gun and sends him off to Iraq.

Other firms take a different approach. One morning, at a military base near the Baghdad airport, a Triple Canopy soldier I was with ran into a friend who had just been fired by the company. The friend had been drunk repeatedly; he'd been caught drinking right up to the hour he was slated for armed escort of a client. The previous day, the friend told us, he went to talk with another American company. Today he was signing a contract.

There is no effective regulation in Iraq of whom the firms hire or how the men are trained or how they conduct themselves. ''At best you've got professionals doing their best in a chaotic and aggressive environment,'' Lyle Hendrick said in an e-mail from Iraq in July, describing his colleagues in private security there. He had spent six months with one company in the country's north and is now with another down in Basra. ''At worst you've got cowboys running almost unchecked, shooting at will and just plain O.T.F. (Out There Flappin').''

I had come to know Hendrick, a tall, soft-spoken, part Blackfoot Native American from South Carolina, while he was on leave in the States. He had been a Special Forces captain, then a private detective; he eventually ran out of money as he let work slip to care for his stepfather, who had had a severe stroke. When he signed on with his first company and, in June of last year, flew into Mosul, a hotbed of the insurgency, a convoy of pickup trucks arrived at the airport to meet the new hires. To his uninitiated eyes, the men in the vehicles ''looked like extras in Mel Gibson's Road Warriors,'' he said. They told him to climb in and to stay ready to shoot while they drove, to watch his sector. ''There was no instruction, no sit-down, no here's how we operate; it was, throw your stuff on the truck and let's go.''

A few months later, he was riding in a convoy, in the back seat of a pickup's cab, escorting an Army Corps of Engineers team to a spot out in the desert, where they would blow up captured munitions. Across the desolate terrain, according to Hendrick and a colleague who was present that day, a white S.U.V. appeared from behind a berm. It was on Hendrick's side, 200 yards away. Hendrick wore a black helmet, tinted goggles and a black shirt, with a kaffiyeh wrapped around his neck and taupe-colored shooting gloves. He leaned out his window clutching a belt-fed light machine gun. The distance kept closing. ''He's coming in! He's coming at us!'' he heard someone on his team call out. He thought, Idiot farmer. He had the best angle; he fired warning shots. He could see the driver dressed all in white. The distance shrank to less than 30 yards. He aimed into the wheels. ''Idiot farmer turned to No, this isn't happening in a fraction of a second,'' he said. All was instinct. He riddled the driver's door and shot into the driver's window. The S.U.V. jerked to the side -- it exploded, ''went from white to a ball of bright orange,'' so close that the blast demolished a vehicle in the convoy, though the men inside weren't hurt. The S.U.V. all but vaporized. It had been packed with explosives -- a suicide bomber. The largest trace left was a scrap of tire. A bit of the bomber's scalp clung to one of the vehicles in the convoy.

Hendrick showed me photographs of the smoky aftermath. He wanted to be sure I understood the kind of circumstances he and his colleagues were dealing with. But he also said, ''This whole thing has brought out some pretty scary characters.'' He mentioned a newspaper article about one of the men he'd worked alongside. The man was arrested when he went on leave back to the States. Apparently the security company hadn't done much of a background check, if it had done one at all; it turned out the man was a fugitive in Massachusetts. He had been charged with embezzlement. He had also violated the terms of a suspended sentence in a separate case, a local paper in Lowell, Mass., explained: he'd been convicted of assault ''for nearly blowing a friend's jaw off during a game of Russian Roulette.''

Mark raised his strong forearms and performed a pantomime of washing his hands and flicking off the water. A manager with Triple Canopy in Baghdad, Mark was sitting behind his desk at T.C.'s base, demonstrating the Department of Defense's attitude about overseeing and policing the private security companies. ''D.O.D. doesn't want anything to do with it,'' he said. ''They don't have time. They don't have the numbers. And State can't investigate incidents. They don't have the investigators. So there's Iraqi law. Not that Iraqi law really exists. Am I going to give up my weapons to Iraqi police? I don't think so. That could get me killed.''

No one knows how many times gunfire from a private security team has wounded a bystander or killed an innocent driver who ventured too close to a convoy, not realizing that mere proximity would be taken for a threat. When they fire their weapons in defense or warning, the teams rarely concern themselves with checking for casualties -- it would be too dangerous; they are in the middle of a war. Besides, no one in power is watching too closely.

And what rules exist seem to be ignored. A C.P.A. decree, which has now evolved into Iraqi law, limits the caliber and type of weapons that private security personnel employ. But I was told by several people in the business that, especially outside Baghdad, weapons like heavy machine guns and grenades are -- perhaps by necessity -- sometimes part of the arsenal.

A few of the major American and British firms, Triple Canopy among them, advocate careful supervision of their business by their governments and possibly, in the future, by the United Nations. They'd like checks on everything from adequate training to human rights violations. They'd like to see their more rash competitors lose their contracts. They'd like to legitimize the work, to remove the remaining stigma that their own men are rogues, mercenaries.