Just as all signs point to Osama bin Laden as the mastermind behind the attack on our country, all signs point to Pakistan as the key to bringing him down.
Pakistan is the key supporter of the Taliban, the primitive Muslim extremists who rule over remote Afghanistan. The Taliban shelter bin Laden, a wealthy Saudi businessman whose terror network aims to show the world that the United States is a spent power.
Getting Pakistan to squeeze the Taliban into expelling bin Laden represents the best chance for our country to grab him without risky military action.
But such Pakistani help is not a sure thing.
The Pakistani connection is unsure, even though Pakistan's ruler, Gen. Pervaiz Musharraf, pledged yesterday to help the United States find the attackers.
Over the last two years, Musharraf chose not to press the Taliban to expel bin Laden, despite strong U.S. urging. U.S. officials believe that Pakistan - one of only three countries that recognize the Taliban government - still trains and aids the Taliban, despite Pakistani denials.
The level of U.S. pressure on Pakistan has risen sharply this week. President Bush says we won't distinguish between terrorists and those who harbor them - or, presumably, those who help the harborers.
Yet, to confront the Taliban over bin Laden, the modern-minded Musharraf will have to confront Pakistani extremists who support them. He will have to risk domestic upheaval.
"This is the moment of reckoning," I was told by Pakistani journalist Ahmed Rashid, author of the best English-language book on the Taliban and its bin Ladin links: "Taliban: Militant Islam, Oil, and Fundamentalism in Central Asia."
"Pakistan has supported a jihad [holy war] culture," says Rashid. "They have to turn it around completely. No more rhetoric, this is the moment they need to clamp down on the fundos [fundamentalists]."
Rashid refers to the tens of thousands of young Pakistani zealots who have crossed the border to train and fight with the Taliban. Educated at religious schools run by extremist Islamic political parties, these youths bring back Taliban values to Pakistan.
I visited one of these schools, Madrassa al-Haqqania, not far from the fabled Khyber Pass to Afghanistan. Many of the top Taliban leaders have trained at the school. The bearded Rashid ul-Haq, son of its founder, told me the school trained students to become good politicians and commandoes.
"We teach the concept of jihad," ul-Haq said. "It's what makes us different."
Many young Pakistani fighters who return from Afghanistan subsequently go to fight against India in Kashmir. This is one reason why the Pakistani army doesn't oppose the Talibanization of its youth.
If Musharraf tries to lean on the Taliban, he risks infuriating Islamic radicals and elements of his army. But now is the moment that Pakistan must make a choice.
Rashid thinks the Pakistani army is strong enough to take on the "fundos."
"National survival is at stake," Rashid says. He adds that he would like the United States to give Pakistan a chance to "press the Taliban to give bin Laden up" before undertaking military action. Pakistan could use the threat of breaking diplomatic relations with Afghanistan, or even withdrawing recognition, which would leave the Taliban totally isolated.
But Washington is asking for more, requesting Pakistani intelligence on bin Laden's movements and the location of his training camps, along with permission to fly over Pakistan and possibly use air bases should military action be needed.
Musharraf is truly in a dilemma. U.S. relations with Pakistan have declined since the days when his country was the staging point for our proxy battle with the Soviets over Afghanistan. We maintain sanctions on Islamabad for its nuclear testing, even as we tighten our ties with Pakistan's arch enemy and neighbor, India.
If Musharraf helps Washington, he can ask us to drop sanctions and embrace Pakistan again. But this first requires him to confront the jihad culture within his country.
The stakes couldn't be higher - for Musharraf or for us.