Washington (CNN) -- The Obama administration has dramatically ratcheted up the American drone warfare program in Pakistan. Since President Obama took office, U.S. drone strikes have killed about a half-dozen militant leaders along with hundreds of other people, a quarter of whom were civilians. As a result of the unprecedented 42 strikes by drone aircraft into Pakistan authorized by the Obama administration, aimed at Taliban and al Qaeda networks based there, about a half-dozen leaders of militant organizations have been killed. The dead include two heads of Uzbek terrorist groups allied with al Qaeda and Baitullah Mehsud, the leader of the Pakistani Taliban, in addition to hundreds of lower-level militants and civilians, according to our analysis.
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Co-authors: President Obama stepped up drone attacks in Pakistan
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They say roughly a quarter of those killed appear to be civilians
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Drone attacks are the least bad option for the U.S. vs. militants, they say
An important factor in the controversy over the drones, put forth by some commentators, is the widespread perception that they kill large numbers of @placeholder civilians.