A combined Russian missile and drone attack on Ukraine overnight killed at least 15 people — including an American citizen — and wounded scores of others, according to Ukrainian officials.

Russia’s increased sense of vulnerability may be the most important result of a recent large-scale Ukrainian drone attack named Operation Spiderweb, experts tell Al Jazeera. The operation destroyed as much as a third of Russia’s strategic bomber fleet on the tarmac of four airfields deep inside Russia on June 1.