Sgt. John Hunt from Blackshear, Georgia, left, and Spc. Brian Kolessar from Middletown, New York, right, both from the 293rd Military Police Company out of Fort Stewart, Georgia, U.S. play jump rope with local children during a patrol in Kandahar City, so
Credit: Kirsty Wigglesworth / AP

Until just a few years ago, America's military focused on tactics any veteran from World War II could recognize: Identify an enemy, apply all available weapons to kill that enemy, and then withdraw, leaving the nation-building to politicians.

In the 21st century, though, America's enemies have made an abrupt shift. On a battlefield crowded with civilians, the military struggles to even identify the enemy. Its high-powered, long-range weapons can't distinguish a radical madrassa student from his moderate classmates. So counterinsurgency's aim is not to wipe out the enemy, but rather to drive a wedge between the population and the insurgents. This creates space for a legitimate government to flourish and isolates the extremists for a more surgical kill. And that, in the end, creates fewer enemies.

"This isn't just the thinking man's war," says John Nagl, a retired lieutenant colonel and a leading counterinsurgency proponent. "This is the graduate level of war." But opposing officers and soldiers say counterinsurgency, or COIN, is a mockery – a sabotage – of the very nature of warfare. "We've essentially turned much of the United States Army into a mix between constabulary forces designed to police unhappy Muslims, and a nation-building corps." That's retired Colonel Doug Macgregor, who says his disdain for counterinsurgency was one thing that prevented him from becoming General Doug Macgregor. "I wonder how they would perform if we suddenly had to fight against someone with real capability? I don't think we would fare very well."

It's an old dilemma. As long as governments have ruled, insurgents have rebelled. In the first century A.D., in North Africa, a Roman Army deserter named Tacfarinas led a rebellion against the Roman Empire. Rather than stand nose-to-nose against the superior Roman legion, Tacfarinas and his band of Berbers blended into the population. He knew Rome's commanders could sort the sands of the Sahara itself before they could sift through the tribal complexities of the region. To kill the rebels they would have to kill everyone.

Much later, British archaeologist-turned-soldier T.E. Lawrence led uprisings in Arabia, Syria, and Jordan on behalf of Britain. He wrote that, in his experience, any insurgency that could enlist just 2 percent of the population as combatants could be very difficult to defeat. "War upon rebellion was messy and slow," he wrote, "like eating soup with a knife."

Here's the trick of counterinsurgency: The hardened 2 percent depend on at least passive sympathy from the other 98 percent. Mao Tse-tung, the leader of the Communist revolution in China, studied Lawrence's tactics and wrote of the local population's relationship with insurgent fighters: "The former may be likened to water, the latter to the fish who inhabit it."

Tacfarinas held off the legion until a Roman commander named Blaesus made a critical discovery: Instead of slashing and burning his way across the countryside, as usual, he offered the war-weary tribesmen a deal. If they turned in their weapons, they would receive a full pardon from the Empire, and Blaesus's troops would protect local villages from any revenge by Tacfarinas in his retreat. And it worked: The population ended its tacit support for the rebels. With deft encouragement from Blaesus, the sands had sorted themselves.

The question, now, is whether that's possible today.