And one of the most unsettling aspects of this and other recent conflicts is that the face of the enemy is often the face of a child,
Sgt. Nathan Chapman was the first American soldier killed in combat in Afghanistan, and the fatal shot appears to have been fired by a 14-year-old boy, reports CBS News Correspondent David Martin.
It was not a tragic fluke, but a precursor of battles to come, said Peter Singer of the Brookings Institution
"Children are present in around three-fourths of the wars out there, including in many of the areas where we're deploying troops now in the war on terrorism." Singer said.
Not just in Afghanistan, where young boys go through al qaida training camps, but in the Philippines, where U.S. Special Forces are aiding in the hunt for members of the Abu Sayeff terrorist group. There are an estimated 300,000 child soldiers worldwide.
"Unfortunately the numbers are growing. They're not decreasing. And I think that it is going to be an emerging threat and the military is going to have to confront this," said Marine Gen. William Catto.
According to Catto, a child's immaturity may actually make him a greater threat than an adult soldier.
"It makes them vicious," she said. "It makes them very, very dangerous because they don't think about the consequence of their actions. They don't have the wisdom to be really afraid," he explained.
Child soldiers are never going to defeat an American force, with all its training and technology, but they can create a nightmare dilemma.
"What do you do if a 14 year old, 12 year old, a 10 year old points an AK-47 at you?" Catto asked.
In Somalia in 1993, that is exactly the dilemma former Army Ranger Keni Thomas faced.
"The minute a weapon is put into somebody's hands they become a combatant. And yes, they were a child soldier, but the point is they were a threat," Thomas said.
Under international law anyone with a gun is a legitimate target, and during a desperate firefight in which 18 American soldiers were killed, Thomas and his fellow rangers did what they had to do - open fire on child soldiers.
"If you were sitting there and your machine gunner gets hit with a round and he's screaming. We pull him off and get someone else on the gun and that person gets hit. We pull him off. You got boys going down around you. These are your buddies and you're watching them go down. Now do you think for one second that any troop that's out there is gonna care about the age of the person that's shooting his men? No.," Thomas said
Added Catto: "I think this is an awful problem, and I don't know, I don't know how we're going to handle it at this point.
Awful because a soldier in combat really has no choice but to shoot a child aiming a weapon at him. Awful because, according to Catto, child soldiers are a threat U.S. troops are not prepared to deal with.