...I spent the night running from room to room, assembling the story in pieces. On the first floor sat the dead elder's brother and nephew, who told me what little they knew of the incident. On the second floor, the ISI officers, over whiskey and lamb tikka, described their work helping U.S. intelligence agents sort out targets from among the images relayed back from the drones. Then there were the two Taliban fighters, whom I had first met in Waziristan in 2007. One had been a fixer for the Haqqani network, skilled at smuggling men and materiel from Pakistan into Afghanistan. The other drew a government salary as an employee of Pakistan's agriculture department but worked across the border as an explosives expert; he had lost a finger fighting the allied forces in Afghanistan. None of the men in the house knew the others were there.

The two fighters described how the militants were adapting to this new kind of warfare. The Taliban and al Qaeda had stopped using electronic devices, they told me. They would no longer gather in huge numbers, even in mosques to pray, and spent their nights outside for safety, a life that was wearing thin. "We can't sleep in the jungle the whole of our lives," one told me. Gradually, a picture of a rare incident came into focus: a deadly strike that had mistakenly taken out a man with no connection to al Qaeda or the Taliban.

This is how it has gone with the drone war, a beat I have covered for six years, first for Newsday and then the New York Times. By the time I left Pakistan in the summer of 2010, the job had become nearly impossible, though it had always been a dauntingly difficult story to tell. The drone campaign is one of the U.S. government's most secret programs. Although the most authoritative study on the subject, by the New America Foundation last year, calculated that 283 drone strikes had occurred in the Afghanistan-Pakistan border region since 2004, Obama never even publicly acknowledged them until this past January. Making matters still more difficult, the targets are in one of the world's most inaccessible areas, one that has traditionally been out of bounds for outsiders and where the state of Pakistan has nominal or no governing authority. It is an environment in which accurate reporting is an often unattainable goal, where confusion, controversies, and myths proliferate.

Although the drone campaign has become the linchpin of the Obama administration's counterterrorism strategy in Central Asia -- and one it is increasingly exporting to places such as Yemen and the Horn of Africa -- we know virtually nothing about it. I spent more than half a decade tracking this most secret of wars across northern Pakistan, taking late-night calls from intelligence agents, sorting through missile fragments at attack sites, counting bodies and graves, interviewing militants and victims. I dodged bullets and, once, an improvised explosive device. At various times I found myself imprisoned by the Taliban and detained by the Pakistani military. Yet even I can say very little for certain about what has happened....