The terrorists wanted to provoke massive and indiscriminate retaliation by the United States that would cause thousands of Muslim civilian casualties and trigger uprisings against pro-Western governments in countries like Egypt and Saudi Arabia, so the safest course was not to retaliate militarily at all. But Americans would not stand for inaction after 6,000 of their fellow-citizens had been burned and crushed to death before their eyes, so domestic political pressure made some kind of retaliation unavoidable.
This dilemma is shaping the United States' strategy toward Afghanistan. The present bombing campaign is being waged in such a way as to minimize civilian casualties, but even so the war must be ended as soon as possible, lest a couple of hundred kids get killed by a stray bomb, the al-Jazeera network brings the pictures out, and the Arab world erupts.
But what kind of success would satisfy the U.S. public's need for catharsis and let Washington declare victory and stop? There are only two possibilities.
Osama bin Laden's head on a stick would certainly do the trick, but he's very hard to find, hidden away in a cave somewhere in a country twice the size of France. He does not use telecommunications that are easily traced. If this war must continue until bin Laden is caught, we could all be a good deal older before it ends.
The other victory big enough to justify stopping the war would be the overthrow of the Taliban regime in Afghanistan. Its leaders are much more vulnerable, for as a government they must remain above ground and yet they are not strong enough militarily to repel a determined U.S. assault.
Day by day, it becomes clearer that Washington has chosen the Taliban as the easier target.
How do you destroy the Taliban quickly and with minimal civilian casualties? Special forces might be able to snatch bin Laden in a daring raid, but they can't defeat a whole army. Giving arms, money, and lots of air support to the warlords of the Northern Alliance might get the job done in the end, but they certainly cannot do it before the onset of winter.
What's left is a direct invasion by U.S. ground forces, perhaps with token assistance from some other coalition members. Most Arab and Muslim countries have given their verbal support but won't be sending military contingents. Invading and occupying Afghanistan would be a high-risk operation, but it would probably succeed and would shut the fighting down before a wheel falls off the ramshackle coalition that Washington has cobbled together.
So how will the U.S.A. invade Afghanistan and carry out a quick kill against the Taliban? It may decide to do it almost entirely by air, using the air-mobile troops of the 82nd Airborne, 101st Airborne and 10th Mountain Divisions to seize first the airports, then the cities and finally the surrounding countryside.
Suitable air bases are available in Russia, Uzbekistan, India, Pakistan and Oman, and there is enough heavy airlift available to fly in troops and supply them for a while. Those air-mobile troops are not now in the region in significant numbers but could be flown in only days before an assault.
If the Taliban are driven from the cities then Washington can declare a victory and stop the war. A new and more respectable Afghan government, given enough money to build an army, buy out the warlords, and start feeding, clothing and educating the desperate population, would probably be able to avoid a long guerrilla war. Bin Laden might not be tracked down for some time, but his ability to operate freely around the world would be ended and U.S. forces could go home.
Of course this scenario wouldn't work out so smoothly in practice but is probably the least bad option.