Drones—or unmanned aerial vehicles, known as UAVs—emerged as a crucial part of war in Ukraine. - genya savilov/Agence France-Presse/Getty Images LONDON—The business of making military drones could be the defense sector’s biggest bubble, the chief executive of rapidly growing arms giant Rheinmetall said. Drones—or unmanned aerial vehicles, known as UAVs—emerged as a crucial part of war in Ukraine and arms makers including Lockheed Martin, Anduril and a host of startups are either producing them or announc ...