Russia’s promise to use lasers to shoot down drones in Ukraine has prompted widespread scepticism that the novel and possibly nuclear-powered weaponry could be deployed on the battlefield or have any significant impact on the war. Yuri Borisov, Russia’s deputy prime minister, told the country’s Channel One television station that the new Zadira directed-energy weapon could destroy targets up to 5km away, and had incinerated a drone in five seconds in a test. But there was no immediate evidence to back up the claim, which was belittled by Ukraine’s president, Volodymyr Zelenskiy, who described it as a “ wunderwaffe ”...