WASHINGTON — AS night fell on what had been a scorching August day in Hadhramaut, Yemen, in 2012, four large explosions shattered the quiet. When the smoke cleared a few minutes later, Sheik Salem Ahmed bin Ali Jaber, a respected and openly anti-extremist cleric, his cousin, a young local police officer named Waleed Abdullah bin Ali Jaber, and three other men, who have been identified in news reports as likely extremists, lay dead — reportedly by an American drone strike.

Late last year I met Faisal bin Ali Jaber, a Yemeni civil engineer, and came face to face with the very real consequences of drone warfare. Faisal’s brother-in-law Salem Jaber and nephew Waleed Jaber were two of the five people killed in the strike. Neither had any terrorist ties. It appears they were simply in the wrong place at the wrong time. Faisal’s journey to the United States Capitol was a remarkable pilgrimage to share his family’s anguish and to remind us of the human toll of the drone campaign that has been a feature of the war on Al Qaeda since the attacks of Sept. 11, 2001.

In a fight against a hidden enemy who operates in lawless safe havens, drones offer many obvious advantages and have taken many dangerous adversaries off the battlefield. But the idea that warfare can be precise, distant or sterile is also dangerous. It can easily blind us to the human cost of those inadvertently killed. And it can cause us to lose sight of the strategic imperative that we not multiply our enemies by causing the inadvertent loss of innocent lives.

There was precious little I could say to Faisal. What I did tell him was that, unlike the terrorists we target, America places a high value on the lives of innocent civilians. I also told him that our personnel make extraordinary efforts to ensure that civilians will not be killed or harmed by any strike. But I could not say whether anyone from the United States government would ever be able to tell him just what had happened, or why.