In striking S-400 launchers in Luhansk, the Ukrainians prolong their campaign targeting the valuable S-400s, which can hit aerial targets as far away as 150 miles.

The Ukrainian army might not have very many M39 missiles. The ones it has, it’s using carefully—firing them at the most valuable targets that also are most vulnerable to the American-made munitions.

In their second-ever strike with the ground-launched M39, on Wednesday, the Ukrainians apparently targeted a Russian air force S-400 air-defense battery in Luhansk Oblast in eastern Ukraine.

Videos and photos from Luhansk depict the detached tail sections of two M39s—and also the aftermath of the purported strike: smoke curling from what Russian social-media users identified as an S-400 battery.

The first M39 strike, on Oct. 17, struck Russian air force bases in Luhansk and outside Berdyansk in Russian-occupied southern Ukraine. The three missiles, each scattering 950 M74 submunitions, wrecked 21 Russian helicopters.