Gen. James Mattis thinks about when, and how, American troops should put their lives at risk.

The lessons of Al-Anbar have shaped Mattis' current views not only about the risks Marines and soldiers must take as they fight block by block but also about how the military views risk in its approach to overall warfare. The core lesson is one he was already preaching: War will always be messy. You can hope to control it, but in the end it is unmanageable. This means always accepting extremely high levels of risk.

Mattis believes that some military and political leaders strayed from this fundamental fact in confronting the Iraqi insurgency. They assumed the new threat could be fought with modern approaches that were not as grueling and painstaking as the counterinsurgency. "The historic lessons were there," he says of the Al-Anbar campaign. "We just tried to apply them to the current situation rather than ignore them and go with the American way of war, which is: Let's hold our breath and pick up our laundry on Wednesday, get a haircut Friday, and get the tanks lined up to attack similar weapons systems."

The public and politicians favor minimal casualties; less collateral damage; and short, winnable wars. This leads to a focus on technological solutions and away from seeing war as a long slog determined by human qualities of intuition, courage, and bravery. "A major attraction of [technology-dependent] war is that few Americans will be at risk," writes military analyst Colin Gray. "The problem is that such a technology-dependent, standoff style is not appropriate for the conduct of war against irregulars."

Drone attacks and PowerPoint presentations give the illusion that war is more manageable than it is, argues Mattis, which is why, as he works to prepare the military for wars of the future, he abolished Effects-Based Operations, a method of planning that sought to determine actions based on quantifiable outcomes. "It is not scientifically possible to accurately predict the outcome of an action," says Mattis in explaining his decision. "To suggest otherwise runs contrary to historical experience and the nature of war."

In making this case, Mattis sounds like the economists who warned against the use of financial instruments like Value-at-risk measurements that sought to quantify risk and make it precise. He quotes Sherman: "Every attempt to make war easy and safe will result in humiliation and disaster," but he could just as easily quote Nobel Laureate economist Kenneth Arrow, who warned of the same problem in economics: "vast ills have followed a belief in certainty."

If you're constantly trying to make war more precise and predictable, you'll promote people who thrive in squeezing out the marginal drop of uncertainty. If you recognize war's essential messiness and the enemy's adaptability, you'll reward mavericks, risk-takers, and people who thrive in uncertainty. They'll have the innovative reflexes necessary for a war that changes block by block, where one minute you may get a handshake and the next you may get a hand-grenade. "Some people feel affronted when something they thought to be true doesn't happen," says Mattis. "If that's the case, then your sense of risk is much higher, and that leads to risk aversion. You need to be able to be comfortable in uncertainty."

Speaking to a new crop of one-star generals, Mattis encourages them not only to take risks by challenging military doctrine but to protect the oddballs in their command. "Take the mavericks in your service, the ones that wear rumpled uniforms and look like a bag of mud but whose ideas are so offsetting that they actually upset the people in the bureaucracy. One of your primary jobs is to take the risk and protect these people, because if they are not nurtured in your service, the enemy will bring their contrary ideas to you."

Counterinsurgency: Inviting More Risk

Only by accepting a higher baseline of risk could the military embrace the counterinsurgency doctrine that is now guiding soldiers on the ground in Afghanistan and Iraq. Fighting an insurgency asks troops to expose themselves to increased threats to their personal safety in order to win over the population, which decreases the long-term risk. The strategy as outlined in the manual (which includes Mattis' Al-Anbar campaign as a key teaching point) is designed around several paradoxes about risk:

• Sometimes the more you protect your force, the less secure you may be.
• Sometimes the more force is used, the less effective it is.
• The more successful the counterinsurgency is, the less force can be used and the more risk must be accepted.
• Sometimes, doing nothing is the best reaction.