A Ukrainian unit, the "Charter" corps, reportedly conducted an underground counteroffensive near Kupyansk, advancing 15 kilometers into enemy rear. The commander, Brigadier General Igor Obolensky, stated that the operation aimed to preempt Russian attempts to infiltrate Ukrainian rear positions via gas pipelines.

The Ukrainian defenders studied the tactics of the occupiers and played ahead of time, seizing the initiative underground. "We watched how the enemy works underground, studied how he does it. The Russians intended to use gas pipelines to penetrate the rear of our troops. Then we went underground ourselves," explained the commander of "Charter," Brigadier General Igor Obolensky. The fighters covered 15 km through tunnels without communication, GPS, and light, having developed their own navigation and life support technologies in advance. The underground maneuver was combined with surface attacks and drone strikes along with the 13th Brigade of the NGU, the "Lava" Regiment, units of the GUR, RDK, "Achilles" and other forces. As a result, the Russians' attempt to enter the rear of Kupyansk was completely thwarted: more than 100 occupiers were eliminated, and another three dozen were taken prisoner.