It is hard to truly understand many war-related activities unless you have been there. The culture of private military contractors is no different.

Up to now the debate over them has largely been policy oriented. Should they be deployed or not? Are they an asset or liability? Cost effective or not? Force multiplier or uncontrollable complication on the battlefield?

But questions such as who they are, what their daily routine is, how their companies actually operate and who can be trusted are not nearly as well explored.

But now we have a book that provides answers to those questions.

Big Boy Rules: America’s Mercenaries Fighting In Iraq, by Steve Fainaru, the Washington Post reporter who won the 2008 Pulitzer Prize for his reporting on private security contractors in Iraq, is a critical yet sympathetic look at the men of Crescent Security Group, a private security firm that will not go down in the history books as an exemplar of professionalism.

Crescent employees commuted daily from Kuwait City to a base at the Iraq border, where they picked up weaponry and set out to provide security for truck convoys.

Fainaru traveled with them to discover their motivations.

Days after he left them in November 2006, five were kidnapped while escorting a convoy. In 2008 they were confirmed dead.

In large part Fainaru’s book revolves around one particular contractor, Jon Cote, a charismatic young ex-Army 82nd Airborne paratrooper who had received an honorable discharge, tried civilian life as a student at the University of Florida, found it lacking and returned to Iraq for the money, adrenaline and camaraderie.

In that sense his story is not that different from veterans of other American wars. Except in this war it is the private contractors, not the soldiers, who are subjected to hisses and insults. That is ironic, considering most private security contractors are former soldiers.

Although Fainaru himself calls the contractors “mercenaries,” he never makes a compelling case that they are in the dictionary sense of the word. He writes, “They were mercenaries — I mean, of course they were — fighting America’s war for money.”

This is true, but it is also insufficient. Compared to the mercenaries of the 1950s and 1960s operating in Africa, today’s private security contractors are but a poor shadow.

Yet Fainaru, while dispassionate, is compassionate and thoughtful, and to his credit he is honest enough to admit that “Over time, the word became as politically loaded, as other Iraq staples, like ‘mission accomplished’ and ‘WMD.’ Defenders of the practice, mostly the companies and their surrogates, parsed the meaning endlessly, like etymologists with guns. Critics dropped it like a cluster bomb.”

What happened to Cote and the other contractors is a tragic and compelling story. It was all the worse given how little was done for them, both by the company they worked for and the government they supported. One of the underappreciated facts of life for private contractors working in a place like Iraq is that while they may make big bucks, they get little else in the way of support.

“With the surge of American troops into Baghdad, the Iraq war had entered a new phase. The mercs, of course, were critical to the campaign, but their vague status was never more important than when they got killed or wounded or disappeared. The system couldn’t handle it; it wasn’t set up for that. In a way, it had a perverse logic; the mercs fought by their own rules and so they died by their own rules. But there was a whiff of shame about how the military and the State Department ignored them so assiduously. It was as if by not counting them — in life or in death — no one had to acknowledge that America had been reduced to relying on a private army to prosecute a war that had entered its fifth year.”

And if you worked for a dodgy firm like Crescent, you ran the risk of making the ultimate sacrifice. On the day the contractors were kidnapped, there were just seven of them guarding a 37-rig convoy stretching nearly one and a half miles. There should have been at least 74 operators, two for each rig.

Even Fainaru, who is not a veteran war reporter, could see how messed up Crescent was. He writes, “I found myself giving Cote advice. I didn’t really think much about it. Crescent, as a going concern, was not even remotely safe; anyone could see that.”

Another industry reality is that there are lots of people who should not be there. They are not the majority, but they are there nevertheless. And, as Fainaru details, it only takes the action of a few misfits to screw things up for everyone else.

Long before the shootings of Iraqis by Blackwater contractors at Nisoor Square, there were enough shootings by security contractors to make the standard justification of the use of lethal force — and the standardized accounts of how and why it was deployed — a mendacious and predictable laughingstock.

As Fainaru notes, “It was the stock explanation for every shooting: warning signals, escalation of force, targeted rounds. That explanation was applied to negligent women, distracted old men, wayward children, anyone who got in the line of fire.”

Many people think if a company has a Web site, cobbles together a few security details and wins a contract, or claims membership in a trade association, that it must really be a professionally run company. Often it just isn’t so.

Free enterprise may be an integral part of the battlefield nowadays, but it is not without costs. Thanks to Big Boy Rules, we now have a far clearer idea of what they are.