THEY ARE PRECISE, small, able to engage a target in relatively large numbers like a swarm of wasps and above all, they are cheap. In Russia’s invasion of Ukraine, drones have cemented their reputation as a potent, hard-to-stop and cost-effective weapon to seek out and destroy targets while simultaneously spreading the kind of terror that can fray the resolve of soldiers and civilians alike. They are also quickly surpassing missiles as the remote weapon of choice because they can be put into any combat theatre in greater numbers much more cheaply. Russia’s unleashing of successive waves of the Iranian-made Shahed...