The engineers at a once-bustling industrial hub deep inside Russia were busy planning. The team had been secretly tasked with building a production line that would operate around-the-clock churning out self-detonating drones, weapons that President Vladimir Putin's forces could use to bombard Ukrainian cities.
A retired official of Russia's Federal Security Service was put in charge of security for the program. The passports of highly skilled employees were seized so they could not leave the country. In correspondence and other documents, engineers used coded language: Drones were "boats," their explosives were "bumpers," and Iran - the country covertly providing technical assistance - was "Ireland" or "Belarus."