Russia’s spring-summer offensive against Ukraine’s fortress belt in Donetsk has stalled after more than a month of fighting. The Institute for the Study of War assessed that Russian forces are unlikely to capture the defensive chain in 2026.
Why it matters
The fortress belt — a 50-kilometre chain of fortified cities from Sloviansk through Kramatorsk and Druzhkivka to Kostiantynivka — is the most strategically significant terrain remaining in Russian-occupied Donetsk. Its capture would give Moscow control of the last major urban centres in the province.
The offensive
Russian forces launched their anticipated spring campaign in mid-March, concentrating attacks from the Lyman direction toward Sloviansk. Moscow’s plan aimed to encircle the Sloviansk-Kramatorsk agglomeration from four directions rather than risk costly frontal assaults.
The 3rd Combined Arms Army, the only Russian force positioned for a direct push on Sloviansk, made tactically significant advances east of the city in early April. It has not gained ground in a week.
Heavy casualties
In one large assault involving more than 500 personnel, Russian forces suffered over 400 casualties — a rate exceeding 80%. Western analysts describe this pace as unsustainable and likely to degrade Russia’s ability to maintain large-scale operations through the summer.
Ukrainian countermeasures
Ukraine has markedly increased its mid-range strike campaign against Russian logistics, military equipment, and troop concentrations since late 2025. These strikes have impeded Russian advances across the theatre and are interfering with the offensive’s supply lines.
The broader picture
Russia’s original objective was to seize all of Donetsk by the end of 2026, with Kostiantynivka targeted for capture by late April. Both timelines now appear out of reach. The offensive continues, but progress is measured in metres rather than kilometres.