The American air campaign in Afghanistan, based on a high-tech, out-of-harm’s-way strategy, has produced a pattern of mistakes that have killed hundreds of Afghan civilians. On-site reviews of 11 locations where airstrikes killed as many as 400 civilians suggest that American commanders have sometimes relied on mistaken information from local Afghans. Also, the Americans’ preference for airstrikes instead of riskier ground operations has cut off a way of checking the accuracy of the intelligence. The reviews, over a six-month period, found that the Pentagon’s use of overwhelming force meant that even when truly military targets were located, civilians were sometimes killed. The 11 sites visited accounted for many of the principal places where Afghans and human rights groups claim that civilians have been killed.