In the battle for Ukraine, the front line is increasingly at a standstill. The reason: rapid innovations in drone technology. From just a few commercial and homemade drones, which the Ukrainians used at the start of the war to locate invading Russian columns, unmanned vehicles now dominate the battlefield. Each side has hundreds of them constantly in the air across the 750-mile front line. Drones can lay mines, deliver everything from ammunition to medication and even evacuate wounded or dead soldiers. Crucially, drones spot any movement along the front line and are dispatched to strike enemy troops and vehicles. ‘Wedding...