Russia bombarded Ukraine’s second-largest city with massive strikes in the early hours of Saturday, its mayor said, one night after Moscow carried out one of the war’s largest aerial assaults on Ukraine.

The covert operation was described as one for the “history books” by Ukraine’s president. According to Ukrainian officials, nearly a third of Moscow’s strategic bomber fleet was destroyed or damaged with cheaply made drones sneaked into Russian territory in the span of a few hours on Sunday.

By Ukraine’s count, that would make this operation one of the most efficient, dollar for dollar, in the history of warfare. No doubt the operatives behind the strike deserve to take a bow. But once the Russian targets stop smoldering at their bases,