(KYIV, UKRAINE) – Ukrainian defence forces have advanced along the Sloviansk sector in the Donetsk region and carried out successful counterattacks in other sectors of the front, according to the Institute for the Study of War (ISW).
The operation, conducted under the name Vivaldi by the Third Army Corps, has achieved an operationally significant objective by disrupting Russia’s effort to conduct a wide encirclement of Ukraine’s Fortress Belt, the ISW assessed on 15th September 2026.
Russian sources have publicly acknowledged that their army no longer controls certain positions east of Lyman, west of Ivanivka, in the northwestern part of Zarichne, and in the northeastern part of Yampil. Previously, Russian forces had claimed to be advancing or maintaining a presence in these areas.
The Ukrainian military has also refuted Russian claims of alleged advances in Sviatohirsk. According to Ukrainian soldiers, Russian troops have increased the number of assaults on the Lyman sector and are amassing forces there, but are suffering casualties due to Ukrainian Armed Forces strikes.
Brigadier General Andrii Biletskyi, commander of the Third Army Corps, confirmed on 15th September that Ukrainian forces had eliminated “enemy pockets” and that the operation had been conducted under a strict regime of information silence.
“The Russians had a plan in the Donetsk sector — to envelop the so-called fortress cities from the north and south,” Biletskyi explained. “The northern pincer has effectively been defeated and destroyed.”
Biletskyi added that the failure of Russia’s plan means Russian forces “will have to assault the Sloviansk-Kramatorsk and Druzhkivka-Kostiantynivka urban areas head-on,” which he described as “far more painful and costly for them.”
Russian losses at this stage of the operation totalled about 1,500 troops, more than 12,000 drones and hundreds of armoured vehicles, artillery systems and other vehicles. Ukrainian unmanned systems units also cut Russian logistics routes, forcing Russian forces to move fuel and lubricants out of Ukraine to Russia’s Voronezh Oblast.
Russian military bloggers have increasingly acknowledged Ukrainian counterattacks around Lyman. Blogger Anatoly Shariy described the situation as a “debacle on the Lyman front,” while the Rybar channel said that “the situation near Lyman is alarming.” Another channel, Dnevnik Desantnika, acknowledged that Russian forces had suffered “an unpleasant tactical defeat,” adding that most Russian troops had withdrawn.
Russian forces have reportedly postponed their objective of seizing Kupiansk until Spring 2027, according to a source reporting on the Russian Western Grouping of Forces, likely due to recent successful Ukrainian counterattacks and advances near the city. Colonel Viktor Trehubov, spokesperson for the Joint Forces of the Armed Forces of Ukraine, stated on 15th September that Russian troops are largely unable to hold their positions on the right bank of the Oskil River closer to Kupiansk itself and are losing territory to Ukrainian forces.
The Third Army Corps reported that Ukrainian troops operating in its area of responsibility struck Russian troop concentrations, a crossing, an ammunition depot, a UAV team, an artillery gun, and a multiple rocket launcher in the Lyman area.
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