"The drone is the ultimate imperial weapon, allowing a superpower almost unlimited reach while keeping its own soldiers far from battle," writes New York Times reporter James Risen in his important new book "Pay Any Price: Greed, Power, and Endless War."

"Drones provide remote-control combat, custom-designed for wars of choice, and they have become the signature weapons of the war on terror."

But America's monopoly on death from a distance is coming to an end. Drone technology is relatively simple and cheap to acquire — which is why more than 70 countries, plus nonstate actors like Hezbollah, have combat drones.