Kyiv’s success during the June 10 attack demonstrates the growing sophistication of the Ukrainian air defense system—but also the increasing pressure the system is facing against the Russian onslaught.

It was the deadliest attack on the Ukrainian capital in almost a year, and came as Moscow has intensified air assaults on the city.

Air raid sirens rang out in Ukraine’s capital as an overnight Russian missile and drone attack killed at least four people and injured 20 others. The attack followed a warning from President Putin that Russia would hit back after Ukrainian drones destroyed several strategic bomber aircraft deep inside Russia.