It was Thucydides who called war “the human thing” – the only definition the Greek historian was willing to offer. War and humanity have evolved together from the beginning. The problem is that 21st-century technology is changing our understanding of war in deeply disturbing ways. “The human [element] is becoming the weakest link,” in the words of an unclassified report from 2003 by the Defense Advanced Research Projects Agency (Darpa), the Pentagon body responsible for the development of technologies for the US military.

The problem is that humans are fallible, and the “pilots” of drones – the unmanned aerial vehicles that form a crucial part of US national security strategy – are no different from anyone else. They sit at their consoles for hours (often eight or more at a time) analysing the video stream that comes on to their screens. This is demanding work, which is why they tend to be young – some of them are as young as 19. A few find the stress too much; chaplains and psychologists are often at hand to help them with the demands of living two very different lives: the online and offline (the world of the military and the world they go home to every night).

But from the military point of view, perhaps, the greatest challenge is that drone pilots can experience “cognitive overload”. The term describes a situation where the amount of information that needs to be processed exceeds the mind’s capacity to store or process the information received. In such situations, either we almost instantly forget the information to hand or we are unable to see whether it contradicts or confirms the information we have stored away. Neuroscientists have begun to monitor pilots’ brain activity, to make them more mindful of collateral damage. By getting them to focus on different things, they are, in effect, rewiring the functioning of their attention system. The pilots are becoming semi-autonomous.