Ukraine’s Third Army Corps says a months-long military operation in the eastern Donetsk region has killed or wounded more than 3,000 Russian troops and brought 125 square kilometers, or about 48 square miles, under Ukrainian control.

The operation, known as Vivaldi, was conducted in northern Donetsk and was kept secret until Sept. 15, when Third Army Corps commander Brig. Gen. Andriy Biletskyi announced the offensive. The operation is part of Ukraine’s continuing effort to defend its remaining positions in Donetsk, where Russian forces have been pushing to capture additional territory.

According to the Ukrainian military, the offensive has produced territorial gains around the villages of Shandryholove and Derylove, while Ukrainian forces have established full control of the Drobysheve area. Ukraine says 50 square kilometers of the territory brought under its control had previously been occupied by Russia.

The operation has relied heavily on unmanned systems rather than sending large numbers of soldiers directly into dangerous areas. The Third Army Corps says its Third Assault Brigade has used heavy bomber drones to drop NC13 strike ground robots, known as “Gryphons,” more than 10 kilometers behind Russian lines.

The corps described the use of bomber drones to deploy the ground robots deep behind enemy positions as a historic first. The systems have been used alongside aerial drones to attack Russian positions and support Ukrainian troops during assaults.

Ground robots have also been used to clear mines and prepare routes for Ukrainian forces. Near Shandryholove, Ukrainian officials said unmanned systems cleared approximately 30 kilometers of routes in two nights. The corps said the same work would have taken conventional Ukrainian sapper, or combat engineer, units about a week and that no sappers were injured during the operation.

“During assault operations, UAVs and ground robotic systems always go ahead of the infantry,” Biletskyi said, describing the role of unmanned systems in the offensive.

The Ukrainian military said the operation’s second phase alone resulted in about 800 additional Russian personnel losses. Overall casualty and territorial claims from the operation have not been independently verified.

The fighting comes as Russia continues offensive operations across Donetsk and other parts of the roughly 1,000-kilometer front line. Ukraine’s General Staff reported 221 combat clashes on Sept. 26, with the heaviest fighting occurring in the Kostiantynivka and Pokrovsk sectors of Donetsk.

Ukraine is also warning that Russia could increase its manpower in the coming months. Ukrainian intelligence has said Moscow could seek to mobilize as many as 300,000 additional troops this year as part of a larger planned call-up extending into 2027. Russian President Vladimir Putin has repeatedly denied that another general mobilization is planned.

President Volodymyr Zelenskyy said Sunday that Ukraine’s military leadership had reported approximately 10,660 Russian troops killed or wounded across the entire front during the previous week. That figure, like the casualty estimates from Operation Vivaldi, has not been independently verified.

The use of ground robots in the Donetsk offensive highlights Ukraine’s growing reliance on unmanned technology as both sides seek to reduce the exposure of troops to mines, artillery, drones, and other battlefield threats.