Inside Tora Bora

LAURA J. WINTER/AP

Wary Alliance fighters enter an al-Quaeda cave near Tora Bora

The 12 bearded soldiers making their way up a pass in the White Mountains of Tora Bora were decked out in flat-topped Afghan caps and flowing shalwar kameezes. From a distance only one detail gave them away as Americans. Afghan alliance fighters—dedicated but largely untrained—walk upright, making themselves easy targets for enemy fire. The Americans were shimmying up the hill on their bellies.

It's no secret that American special-operations forces have been in Afghanistan, but late last week they quietly made their way to Tora Bora, to the very front of the front lines. The...