The Pacer: How Bin Laden's Daily Stroll Gave Him Away

It began with an innocuous, catch-up phone call. Abu Ahmed al-Kuwaiti — the pseudonym of the Pakistani the United States believed was Osama bin Laden's main courier — took a call from an old friend who simply wanted to know where he had been. The call gave American intelligence what four years of hunting had not: the courier's cellphone number.

From there, as the Washington Post reported in May 2011, the trail tightened fast. Kuwaiti was tracked to a large compound in Abbottabad. The residents were clearly allergic to electronic surveillance: the main three-story building had no phone lines and no internet, and whenever Kuwaiti left to make a call he reportedly drove some 90 minutes away before even placing a battery in his cellphone.

But satellite imagery gave the analysts something the eavesdroppers could not. Most days, a tall man emerged to walk the courtyard for an hour or two — back and forth, day after day. He never left the compound. Imagery never gave a clear view of his face. The analysts started calling him "the pacer."

Was the pacer bin Laden? A decoy? A setup? The assessments ranged widely — several put the chance at 60 to 80 percent; the head of the National Counterterrorism Center put it around 40. It was a gamble either way.

On May 2, 2011, the gamble paid off. The tall man pacing behind those walls was the fugitive the world had hunted for a decade — given away, in the end, by the one habit he could not hide from the sky.