Russian forces have made fresh tactical advances into Kostiantynivka, the Institute for the Study of War (ISW) assessed on 10 June. The city sits at the southern tip of Ukraine's Donetsk Oblast Fortress Belt — Moscow's main effort for the spring-summer 2026 offensive. Russia missed its own May deadline to take the city, and the wider fortified chain stays out of operational reach.
Two named Russian formations have pushed into eastern Kostiantynivka from the south, Ukrainian military observer Kostiantyn Mashovets reported on 10 June. He identified them as the "Bakhmut" tactical group and the "Dzerzhinsk" (Toretsk) tactical group. The "Bakhmut" group is built around Russia's 3rd Army Corps (AC) under the Southern Grouping of Forces. The "Dzerzhinsk" group operates in the area of responsibility of the 8th Combined Arms Army (CAA) of the Southern Military District. It likely includes elements of five CAAs, the 3rd AC, and Russian naval fleets, Mashovets noted.
Elements of the "Bakhmut" group pushed from Stupochky through Novodmytrivka into northeastern Kostiantynivka. They also advanced along the T-0504 Pokrovsk-Bakhmut road as far as the city's railway station. The "Dzerzhinsk" group moved from Illinivka, south of the city, into areas stretching from northwestern to southwestern Kostiantynivka near the railway station. Mashovets assessed that it has likely achieved a tactical breakthrough in the western, central part of the city. Forward assault elements of the two groups now stand roughly two kilometers apart. Russian forces have so far failed to seize the railway station. Ukrainian troops cleared the village of Dovha Blaka southwest of the city of Russian infiltrators.
ISW noted that Russian forces opened the campaign for Kostiantynivka in August 2025 after seizing the majority of Chasiv Yar and Toretsk, with Toretsk alone running to roughly 26,000 Russian casualties. The first Russian troops infiltrated Kostiantynivka itself in October 2025. Russia has since worked into at least 12.69% of the city. Ukrainian officials reported earlier this spring that the Russian command had set a May 2026 deadline for the seizure. That deadline has come and gone.
Russia has poured forces into the effort regardless. Ukrainian Commander-in-Chief Oleksandr Syrskyi said on 2 May that Russian activity in this direction noticeably increased in April. Russian units in the area had reportedly been replenished by 80% as of 6 June, ISW noted. The Russian command reportedly redeployed elements of the 70th Motorized Rifle Division to the Kostiantynivka-Chasiv Yar area last December. The redeployment likely came in preparation for the spring push.
ISW assessed that Russian forces will likely keep infiltrating throughout Kostiantynivka. They will likely consolidate positions in parts of the city while suffering high casualties. Russia's 3rd AC northeast of the city appears to be struggling to dislodge Ukrainian forces from Chasiv Yar. That inhibits any move to envelop Kostiantynivka from the north. A Russian milblogger claimed on 9 June that Ukrainian forces recently counterattacked near Chasiv Yar. The milblogger added that Ukraine still holds Podilske and Mykolaivka west of the town.
The northern flank of the Fortress Belt is also bogged down. Russia opened its spring-summer 2026 offensive with mechanized assaults around Lyman. Those assaults signaled intent to advance on Sloviansk from the northeast. They produced no significant gains, ISW noted. The Russian command likely shifted weight south to Kostiantynivka. Russia's Western Grouping of Forces covers the front from Kupiansk through Lyman. It likely lacks the combat power to push on Sloviansk while balancing operations toward Kupiansk and Borova.
Ukraine's Volyn Oblast will install anti-drone nets along sections of roads near the border with Belarus, the acting head of the Volyn Oblast Military Administration, Roman Romaniuk, announced. Volyn Oblast borders both Belarus and Poland in the northwest of Ukraine.
The anti-drone nets address the localized threat of FPV-class drones that could target road traffic on this corridor.
In April 2026, Ukrainian President Volodymyr Zelenskyy reported the expansion of military and road infrastructure in Belarus near the border with Ukraine, creating a potential security threat.
Ukrainian intelligence has recorded the construction of new roads, military camps, training grounds, bases, and artillery positions.
Russia has already used Belarus as a launch pad for signal-relay balloons that help its drones reach Ukrainian cities.
In 2025, Russian drones launched from Belarus had already crossed into Polish airspace when 19 Russian Shahed-type drones entered Poland, and Warsaw invoked NATO Article 4 for the first time in the war.
Meanwhile, the Institute for the Study of War (ISW) has assessed that a Belarusian ground invasion of Ukraine remains "very unlikely," but Russia may continue to use Belarusian airspace to hit Western Ukraine — and, as 2025 demonstrated, to test NATO's eastern flank response.
"Risks from the neighboring state remain, so Volyn Oblast continues to systematically prepare for any possible challenges," Romaniuk said.
Ukraine is currently installing engineering barriers, strengthening defensive positions, and implementing new security measures.
"One of them will be the installation of anti-drone nets on individual sections of roads, including on the territory of Shatsk hromada," the Shatsk hromada quoted Romaniuk as saying.
Romaniuk added that Volyn today is one of the best-prepared border regions of Ukraine and that this work must be continued.
© Eric Lee/The New York Times
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