The Russian army that rolled into Ukraine on the morning of Feb. 24 brought with it some of the world’s most powerful, and indiscriminate, artillery. Now the Ukrainian army has captured at least five of these TOS-1 thermobaric rocket-launchers—and reportedly has fired one of them back at the Russians.

Serhiy Bratchuk, a spokesperson for the administration of Odessa, told Victor Kovalenko, a former Ukrainian soldier and journalist, that Ukrainian troops aimed one of their ex-Russian TOS-1s at Russian positions around Izium, in eastern Ukraine near Kharkiv, on or before April 5.

TOS-1 with its 220-millimeter “flamethrowing” rockets is a uniquely destructive system, but one barrage from one captured launcher isn’t militarily significant. As a statement, however, the purported reversal—Ukraine pointing one of Russia’s most fearsome weapons back at it—is striking.

For troops and civilians on the ground, thermobaric munitions can be terrifying. They burst over their targets, spreading a fuel vapor, before exploding and igniting the fuel, creating a pressure wave that’s twice as powerful as that from a conventional artillery shell.

“A fuel-air explosive can have the effect of a tactical nuclear weapon without residual radiation,” Lester Grau and Timothy Smith explained in a 2000 article in Marine Corps Gazette.

The pre-war Russian army possessed around 100 TOS-1s and deployed a significant number of them in its wider war on Ukraine. We know this because the Kremlin has made a point of showcasing the TOS-1s in its videos—and because Ukrainian missile teams have recorded videos of themselves knocking out several of the launchers and support vehicles.