A dramatic duel between a Russian “flamethrowing” rocket launcher and Ukrainian artillery somewhere in eastern Ukraine recently underscores a brutal truth about the fighting along that front, 100 days into Russia’s wider war on Ukraine.

It’s an artillery fight. Big guns and rocket launchers shoot at enemy troops while the enemy’s own big guns shoot back. Whoever shoots more, farther, and faster should have the upper hand.

The duel played out during a video shoot by Russian propagandists. The video’s host stood next to a TOS-1 thermobaric rocket launcher, bragging about the “demoralizing” effect of the 220-millimeter-diameter rockets.

The TOS-1 is one of the more terrifying weapons in the Russian arsenal. Thermobaric munitions burst over their targets, spreading a fuel vapor before exploding and igniting the fuel—and 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 Russians seem to have deployed to Ukraine the majority of the roughly 50 TOS-1s they had before the war. The Ukrainians have destroyed several of the 45-ton, 30-round launchers and associated support vehicles and captured others—and have fired at least one captured launcher back at the Russians.

But TOS-1s still are active along the front. They’re especially useful as the Kremlin narrows its war aims and focuses its remaining forces on surrounding and cutting off Severodonetsk, the last city on the eastern bank of the Donets River in eastern Ukraine’s Donbas region.

The Ukrainians defending Severodonetsk and the adjacent city of Lysychansk on the other side of the river have dug in deep. Ukrainian defenses are stiffest around an old chemical factory in Severodonetsk.

The factory with its basements, tunnels, and Cold War-vintage fallout shelters is a virtual fortress, just like the Azovstal steel plant in Russian-occupied Mariupol in southern Ukraine was before the Russians finally starved out the local garrison last month.

The TOS-1 is one of the best weapons for rooting out those underground positions. “Since a fuel-air mixture flows easily into any cavities, neither natural terrain features nor non-hermetically sealed field fortifications … protect against the effects of fuel-air explosives,” Grau and Smith wrote.

Thermobaric rockets are part of the mix as concentrated fires help Russian troops advance around Severodonetsk. “Russia has achieved these recent tactical successes at significant resource cost, and by concentrating force and fires on a single part of the overall campaign,” the U.K. Defense Ministry stated.

It should come as no surprise that Russian media chose to highlight a TOS-1 battery somewhere in the east in recent days. And it also should come as no surprise that the Ukrainians likewise took an interest in the TOS-1.

In the video, the TOS-1 fires one rocket—standard practice, as the crew would wait to gauge the accuracy of the first shot before firing a full salvo. Less than a minute later, there’s the sharp sound of incoming Ukrainian artillery, which apparently misses.

The video crew flees. The TOS-1 fires more rockets. More Ukrainian artillery is audible before the video ends.

It’s unclear whether the TOS-1 survived the Ukrainian “counterbattery” barrage. There were factors working against the Russian launcher. The TOS-1, while powerful, lacks range: six miles is the maximum.

Six miles isn’t very far in an artillery fight. Even the oldest Ukrainian howitzers can shoot farther than that. The latest American-made M-777s can fire out to a distance of 19 miles.

To be clear, Russian guns and rockets outnumber Ukrainian guns and rockets, especially in Donbas. But the Ukrainians have some advantages in a counterbattery fight—in particular with TOS-1s.

Kyiv’s forces far more than Moscow’s forces have learned to deploy drones, including military models, off-the-shelf quadcopters, and custom-made octocopters. Many hundreds of them. Drones can spot Russian artillery and help walk-in return fire.

The Ukrainian army also deploys American-made counterbattery radars. The radars detect enemy artillery fire and instantaneously—and precisely—trace it back to its origin.

The Russian army has counterbattery radars, too, of course. But the Ukrainian army benefits from steady supplies of fresh radars from foreign donors. The Ukrainians since February have received no fewer than three dozen new counterbattery radars from the United States and other foreign allies.

The Ukrainian counterbattery system, dramatically on display in that Russian propaganda-gone-wrong, should improve in coming weeks as the first High-Mobility Artillery Rocket System launchers arrive from the United States. A truck-mounted HIMARS can fire six M30 rockets out to a distance of 43 miles, well beyond the range of almost all Russian guns and rockets.

Pair HIMARS with drones and radars and you’ve got a highly effective counterbattery system. It’s possible the TOS-1 in the video escaped the Ukrainian shelling. Pretty soon, however, dodging counterbattery fire could get a lot harder for the Russians.