The US military is now poised to enter the second phase of its Afghanistan campaign - the pursuit and destruction of slivered remnants of Taliban and Al Qaeda forces.
That's unlikely to be a simple mop-up operation. After all, the Soviet Union controlled many Afghan cities and much of the country for years, yet came to grief in the mountainous redoubts to which the Taliban is now retreating.
But in their glory years, the mujahideen had both the civilian population and large stocks of US weapons behind them. Today, the fighting men in the caves have neither. Their adversaries include not only US special-operations groups, but also local warlords who sense that history is no longer on the Taliban's side.
"This is about dividing the spoils now. I think you'll see simmering levels of violence for some time," says Peter Singer, a former Pentagon action officer in the Balkans who is now a fellow at the Brookings Institution here.
From the beginning, the White House and Pentagon leadership have counseled patience for what is a multifaceted military effort. They say they weren't pessimistic in the first month of war, when things seemed to be moving slowly. They insist they're not euphoric now, as the Taliban has apparently gone from government to ground in a week.
Still, there's apparent relief in top circles that the overall military strategy, to this point, has worked. The combination of US air power and proxy ground forces was designed to pit American strengths against Taliban weaknesses. It's a bob-and-weave approach that targeted the Taliban's cohesiveness - its "center of gravity," in military terms.
That center of gravity has now cracked. The way in which the Taliban retreated from Kabul and other territory in the north indicated that communication and force discipline had been lost. To a military force, loss of self-control can be a far graver matter than simple loss of territory.
In their fallback from Kabul, many Taliban troops, and probably their Al Qaeda allies as well, mixed on the roads with a fleeing civilian population. Reports indicated that they were hijacking vehicles from aid groups in their efforts to flee.
On one hand, this confusion made it difficult for US aircraft to attack any flushed-out fighters. But on the other, it was a sign that Taliban fighters had lost all ability to operate in any kind of unit, at least for the moment.
"It is indicative of a loss of that discipline and coherence," said Defense Department spokesman Rear Adm. Craig Quigley, at a briefing on Nov. 14.
The US did not plan a north- south strategy, in which the Northern Alliance would roll into Kabul, pushing the Taliban into the southern part of the country. That's what officials say now, anyway. They have described the military strategy as a more general tightening of the vise. That's an analogy that might apply to the second phase of the fight, as well.
Osama bin Laden himself has described the retreat from Kabul as a trap to lure US and British troops into the countryside, where the Taliban can fight them on their on terms. Generations of Western military forces - not just the Soviets - have found frontal attack on Afghan rebels to be deadly and as frustrating as fighting ghosts.
But since Vietnam, the US military has learned to fight on its terms, not the other force's, as much as possible. That makes introduction of large numbers of US ground forces in a timely manner possible, but unlikely.
At the beginning, phase 2 is likely to look a lot like phase 1: airstrikes, combined with an increased effort by small groups of US Special Operations Forces and a hope that internal strife and defections will erode the Taliban from within.
"The pressure is going to have to stay on, not just in Afghanistan but elsewhere, because the terrorist networks are spread across the globe," said Secretary of Defense Donald Rumsfeld in New York on Nov. 14.
Military analysts say the Taliban collapse in the north happened far too quickly for it to be a trap. Dispersion into the hills could well presage a lengthy and draining guerrilla war, or it may not. The outcome turns on how many fighters the Taliban have left and how committed they are.
Many of the Taliban's Afghan supporters joined only as the regime gained power. While the so-called Arab Afghans - Al Qaeda volunteers from Pakistan and elsewhere - are likely to remain committed, local fighters may fade into the countryside as Taliban power ebbs.
"We're going to find out how large [their] solid base of support is," says Jack Spencer, a military analyst at the Heritage Foundation.
That solid base could fight on for years. The US, in the end, may have to send in its forces to root out the remnants of the terror network.
But Taliban cohesion is now such that leader Mullah Mohammad Omar and his ally, Mr. bin Laden, may be at risk from former followers as much as from US special-operations teams. A disaffected warlord could use the pair as poker chips, turning them in for US cash and gratitude.
"This is the most optimistic I've been about [the capture of bin Laden]," says Mr. Singer.