Why are Moscow’s air defenses struggling to stop drone attacks? And why are oil refineries so vulnerable to Ukrainian strikes?

On June 16 and 18, Ukrainian drones broke through defenses in southeastern Moscow and knocked out both primary oil distillation units at the Moscow oil refinery. During the second strike, several fuel storage tanks caught fire, and smoke from the blaze blanketed the surrounding residential neighborhoods. In carrying out the attack, Ukraine’s Armed Forces achieved several objectives at once: they continued their campaign of strikes against oil refineries; demonstrated their ability to penetrate R...