Wars are vastly expensive in blood and treasure. The outcomes are always uncertain, and continued public support is not guaranteed. Witness Iraq and Afghanistan. Faced with the threat of terrorism, the Obama Administration has "decisively embraced the drone… as a cheap, safe and precise tool to eliminate enemies." But the Obama Defense Department isn't the only one adopting unmanned drones for reconnaissance and, ultimately, for targeted killing. Is it legal? Will the US be vulnerable when China, other countries or terrorists develop their own technologies?