When fighting begins, military establishments are nearly as eager to observe and record the results as to win. This emphasis is natural, since claims about what did and didn't work may be used for decades afterward to settle arguments, justify new weapons, and affect military doctrine. Long before the first bombs were dropped on Afghanistan, some of the Pentagon's official historians had been invited into the building to observe the proceedings.

The process of interpreting battlefield results can be surprisingly slow. William S. Lind, a military analyst, has observed that it took several years after the end of the Gulf War for the American public to realize that much of Iraq's Republican Guard had escaped. The full answers about the first stage of this war, the battle against the Taliban, may take as long to emerge as the Bush Administration says the war on terrorism will last—again, years. But it is already clear what one significant question will be: Why did the Air Force change its approach so dramatically in the early days of the war?

That there was a change is obvious. Last October the Air Force for a week or two followed what had been its classic twentieth-century doctrine of "strategic bombing." A strategic air campaign is intended to weaken an enemy's military force indirectly, by attacking its underpinnings, rather than directly, by attacking the force itself. Therefore the United States blew up airfields, attacked radar sites, and destroyed such command-and-control centers as it could find.

By late October the bombing campaign had been retooled as something more like "close air support." This is the Army's term for what it thinks the Air Force never wants to provide, in which bombers and attack planes serve as a kind of mobile artillery, aiming right at the enemy soldiers and tanks. This kind of attack requires more flexibility and faster response times than strategic bombing does; targets may change minute by minute, rather than being picked days in advance. It also requires closer coordination between air and ground forces, and in effect makes the Air Force an adjunct of the Army. The ground soldiers are the ones choosing the targets, and the pilots are supposed to respond right away.

By late October news accounts were referring to air attacks on the Taliban as being directed by Army Special Forces soldiers plus para-military agents from the CIA working with Northern Alliance ground troops. At this point the war against the Taliban became a rout. With guidance from the ground, Air Force planes could drive Taliban soldiers out of protected positions, destroy their tanks and equipment once they were on the move, and quickly make it impossible for them to fight on.

The question is why the Air Force started behaving this way. It would be nice if the answer were, simply, Because it made military sense. But in previous battles coordinating ground and air efforts took much longer than this. In a number of recent interviews I found no one who was sure of the explanation, but I identified two main hypotheses.

One view, favored in the Air Force, is that this new collaboration between air and ground forces was a natural response to the arrival of new technology— specifically, reliable precision-guided weapons. American ground troops could use sighting devices to get the exact coordinates of a target as small as a tank; bombs with the highly reliable and relatively cheap JDAM ("joint direct attack munition") guidance system could use those coordinates to follow the target through wind, smoke, and cloud.

"No one expected [this combined approach] to work out as well as it did," a retired Air Force officer told me. "No one in the Air Force, and no one in the Army. We've had the ability for quite some time. But we never practiced having a sergeant on the ground get a B-52 to attack a target from thirty-five thousand feet." One reason this was never practiced, he told me, was that "the possibilities for error are unlimited." Indeed, the first major "friendly fire" episode in the war, in which five Special Forces soldiers were injured and five Northern Alliance soldiers were killed by an American JDAM bomb, resulted from a targeting error. The spotters relaying the target's coordinates to the bomber circling overhead mistakenly sent the coordinates of their own location. But this was the exception. The Air Force man continued, "They got real good at it, the green-suiters [in the Army] and the blue-suiters [in the Air Force]. Instead of hitting a cave and having nothing happen, you'd hit a cave and Taliban would come streaming out. It was inconceivable just a little time earlier that they could work that closely together."

A less uplifting interpretation of this view is that the Air Force began cooperating with the Army because in doing so it could outflank the Navy. During the first two weeks of bombing the Air Force's presence was mainly big bombers operating from miles up. This fit the strategic-bombing doctrine and also fit local realities, because there were no nearby bases from which Air Force fighter or ground-attack planes could operate. But it left the tactical role—for fighter and attack aircraft—to naval planes operating from carriers. Past conflicts would lead to the natural assumption that these more agile aircraft, operating closer to the ground, would do the precision-bombing work. By showing that its old, lumbering bombers could hit tanks and troops with the help of spotters, the Air Force created a new role for itself.

The other main view is that the Air Force was neither discovering how to cooperate with the Army nor seeing that it could match the Navy's role. Instead it was responding to direct orders to change its behavior, presumably issued by Secretary of Defense Donald Rumsfeld. The evidence here is circumstantial. Until September 10 Rumsfeld was described as embattled within the Pentagon, because of his impatience with bureaucratic gamesmanship and interservice jockeying. Both before and after September 11 he expressed to friends his exasperation with the hidebound nature of the services' leadership. In the first two weeks of the war, according to this view, he saw the real-world harm caused by the attitudes he had spent months complaining about.

One retired Army officer describes the first stage of the war as having been conducted "stovepipe" fashion, with separate chains of command for each service. The ground forces would relay their observations and targeting requests up the pipe to the senior Army command. The Army commanders would relay the requests to senior Air Force officials, who would pass word down to the bomber crews. Hours or days after the original request, bombs would fall where targets might no longer be.

It would be in keeping with Rumsfeld's personality and record to order the Air Force and the Army to stop fooling around and start hitting targets. If the campaign in Afghanistan continues to be viewed as a success, many people will claim credit for the crucial change in policy. As long as the military applies the concept of fast coordinated campaigns, the parentage of the idea may not matter. Still, I would like to find out what it was.

Of course, it is possible that the campaign will not lastingly be seen as such a victory. William Lind, the military analyst, and G. I. Wilson, a colonel in the Marines, deserve a hearing on this point, because they have been prescient before. For instance, in a book chapter written with Marine Corps Major John Schmitt last summer, two months before the terrorist attacks, they said, "Arguably the most serious direct and immediate threat to U.S. national security today is not another state, rogue or otherwise, but the transnational terrorist organization Al Qa'ida."

Lind and Wilson and three co-authors had warned in an influential 1989 Marine Corps Gazette article that the United States would be vexed in the future by enemies that avoided attacking our big, well-equipped military and went straight for our cities and economic base. We would be all the more frustrated in attempting to respond, they said, because the American military knows everything about fighting other countries and armies but not about fighting enemies that are separate from any state. To the authors' chagrin, in February an Internet magazine that claims to represent al Qaeda cited that article as having helped to give the terrorists their insight that a "new type of war presents significant difficulties for the Western war machine."

I recently asked Lind and Wilson what they made of the war so far. Each emphasized how little was known for sure and how wrong any given interpretation could be. That said, they went on to sound a distinctly non-triumphal note. Lind warned that vanquishing the Taliban, however satisfying, probably accomplished less in the long run than we thought. "When the Taliban had a state, we were able to fight it," he wrote recently, in an unpublished paper that he showed me.

But its essence was never being a state, much less having facilities we could blow up with missiles. The Taliban was a movement, a non-state actor made up of people with a shared world-view ... Those people have not been killed, nor taken prisoner (with a very few exceptions), nor driven out. They are in Afghanistan, waiting ... And, now that the Taliban is not a state, we cannot fight it.

He was also highly skeptical that the spotter-bomber combination that worked so well in Afghanistan would make much difference anywhere else. "It's what I might call the ultimate French dream," he said, referring to France's interwar theory that war could be reduced to forward observers and artillery. The reason it worked in Afghanistan, he said, is that the Taliban had alienated most of the population, so spotters could travel easily. "There are not a lot of situations like that," he told me. "If the population is hostile, your little team has a very short shelf life."

Wilson said that if he were writing the 1989 paper today, he would emphasize the sheer economic impact terrorist attacks can have. "Look at all the money and energy we're tying up trying to improve airport security," he said. "I would also have focused more on the ways in which the basic institutions in our society can be turned into vehicles for destruction." Wilson sounded as if he had been more surprised by the anthrax scare, with its devastating effect on the postal service and the businesses that rely on it, than by the September 11 attacks. "I wish I had focused more," he said, "on the way one lone individual, a Kaczynski type of guy, can leverage our institutions and systems against us."

On only one point did Lind and Wilson line up with the Pentagon officials celebrating success in Afghanistan: technology provides new possibilities in conflict. But ideas and behavior, Lind and Wilson emphasized, are still more important than machines—the terrorists' idea of turning airliners into weapons; the U.S. military's idea, whatever its origin, that B-52s could be directed by soldiers on the ground. This war of ideas may be just beginning.