When the stranger unbolted the cell door and whispered for them to hurry, Rahim assumed that somewhere in the prison a fight must have broken out. It was the middle of the night, and normally the heavy metal door remained locked until the morning call to prayer. For the past five months, Rahim had shared this cell, in Kandahar’s Sarposa Prison, with five other captured insurgents, two of whom he’d fought alongside in the fiercely contested district of Panjwai. Now, from where they lay on old blankets and cushions on the floor, all five gazed uncertainly at the man standing in their doorway. "We are your friends," the man said. "There is a tunnel over here. Come quickly and get inside it."

Rahim and his cellmates stepped into the prison’s dimly lit lime green corridor. At the passageway’s far end, a metal gate sealed the cell-block entrance. Every ten feet or so, solid black doors led to more communal cells. Nearly 500 Taliban occupied this part of Sarposa, called the political block. Some were military commanders and shadow-government officials, others hardened foot soldiers and young recruits. Their arrests represented years of effort by coalition forces to quell a resuscitated insurgency and impose some semblance of law in one of the least stable regions in Afghanistan. Following the stranger down the long hall, Rahim noticed that most of the cells were now empty.

The group made its way quietly but without too much concern for the guards; Sarposa’s officers seldom patrolled the political block. Once in the morning and once in the evening they came to take attendance; otherwise, the Taliban were left to care for themselves. Within the block’s three contiguous wings, a council of elders resolved disputes, prisoners knitted blankets and clothes for those lacking them, and in an enclosed courtyard a detained imam led prayers five times a day. The cells themselves were lavishly furnished with comfort items delivered in large plastic bags by visitors every weekend—cushions, blankets, rugs, electric fans, and lamps. Periodic security checks invariably uncovered mobile phones secreted in the floors and walls. Since the Taliban consider music un-Islamic, radios were nonexistent. Instead, for amusement, inmates flipped over metal soup bowls and beat them in time with religious chants. As Rahim and his cellmates moved down the corridor, their footfalls were mu±ed by such a drumming.

American soldiers interrogate a suspected Sarposa fugitive.

Near the gated entrance at the end of the corridor, the stranger ushered the group into a cell adorned with old maps, embroidered tapestries, and a mirror hanging from a coatrack, decorated with an etching of an AK-47. A blue carpet had been pulled back from one corner of the cell to reveal a triangular hole in the floor. Rahim approached the jagged opening and peered inside. The striated walls tunneled down through half a foot of concrete, through an equally thin layer of foundational stone, and finally through some six feet of brown earth. Several prisoners gathered at its edge. Some were young fighters; a few were geriatrics or amputees. Rahim was in his early twenties but had lost his left leg a year earlier to an IED and now used a prosthesis. He watched an old man toss his crutches aside and lower himself into the floor. Rahim did the same.

The dirt below was dry and soft. It was so crowded that when Rahim fell to his knees and started to crawl, he bumped into the man ahead of him. As he inched forward, another prisoner jumped into the hole behind him. On all fours, his back scraping against the ceiling, Rahim wormed his way forward. Whoever had burrowed the passage had installed a series of light bulbs that hung from an electrical cord. But by now many of the bulbs had shattered, broken by passing prisoners, and pieces of glass littered the tunnel floor. After a few hundred feet, it was almost completely dark.