How Al Qaeda Slipped Away: The war in Afghanistan is widely regarded as a great success. But one key objective was not achieved. The inside story of Al Qaeda's mass escape.

Byline: Rod Nordland, Sami Yousafzai and Babak Dehghanpisheh

The Afghan foot patrol was so hot on the trail of fleeing Qaeda troops that the pursuers could literally smell blood. Across the high passes of the Tora Bora range they raced, with blankets drawn over their shoulders and their turbans wrapped around their faces against the freezing December wind. They came upon a man's severed leg, its stump still oozing blood. The owner couldn't have gotten far. Ahead was a high intermontane valley, and beyond it an even more formidable barrier, the Spin Ghar range--the White Mountains. The fugitives were as good as dead or captured. American B-52s and attack helicopters were plastering the hillsides; some 1,500 pro-Western Afghans had joined the chase, and on the far side of the White Mountains the Pakistanis had ostensibly closed the border.

The pursuit team, under the command of the pro-U.S. warlord Hazrat Ali, finally outran its quarry. In a remote valley strewn with discarded blankets and empty ammo clips, Ali's men fought a three-hour fire fight with 30 or so foreign guerrillas, all of whom had fled from the siege of Tora Bora. The Afghans killed most of the Qaeda fighters that day, Ali says. Then they returned home to proclaim victory.

But even the boastful Hazrat Ali acknowledges that the dead were only stragglers, and that other Qaeda fighters got away. Some Afghans now claim that Qaeda leaders paid off another (supposedly pro-American) warlord to allow safe passage. Others blame American forces: the B-52s, they say, dropped their 2,000-pound ordnance on the wrong escape route. Still others, including Ali, claim that mysterious black helicopters swept in, flying low over the mountains at night, and scooped up Al Qaeda's top leaders. (Pentagon sources suggest the choppers were theirs, dropping or plucking up Special Forces.) What is not in dispute is that by mid-December, 1,000 or more Qaeda operatives, including most of the chief planners and almost certainly Osama bin Laden himself, had managed to escape. Efforts to capture them since then had one notable success--the capture of key operative Abu Zubaydah in the Pakistani city of Faisalabad in late March. But most of the top echelon and even rank-and-file fighters are still on the loose.

What went wrong? American officials, both civilian and military, prefer to focus on what went right. In only three months, U.S. forces and Afghan proxies managed to rout the Taliban and deprive Al Qaeda of its base, at modest cost in American lives. American officials concede that there was a mass escape from Tora Bora--as well as a broader exodus by various routes into Pakistan and Iran--but insist that Al Qaeda now is crippled and too busy running to do much damage. "Perhaps we could have got them wholesale," says one senior Defense official. "Now we're doing it retail. In the end, it doesn't make much difference. We're getting them."

But it does make a difference. Some European and Arab intelligence experts believe, in fact, that Al Qaeda has mutated into a form that is no less deadly and even more difficult to combat. "We are confronted with cells that are all over the place, developing in a very horizontal structure without any evident big center of coordination," a top European counterterrorist investigator told NEWSWEEK. "Our operational evaluation today is that the threat is a lot greater than it was in December. That is to say, the worst is ahead of us, not behind us."

At a time when leaders in Washington are agitating to move on to the next war--to remove Saddam Hussein--it's perhaps surprising that few if any are critiquing the Afghan campaign. Criticism is deemed to be almost …