Key facts
- Russian forces are engaged in an ongoing battle for control of Kostiantynivka in Donetsk Oblast.
- Infiltration attempts into the city began in late October 2025, with advances in southeastern and eastern areas.
- By early 2026, Russian forces were assaulting southwestern Kostiantynivka and had gained control of the Kleban-Byk Reservoir.
- Ukrainian forces are working to protect supply lines and repel Russian advances.
The Battle of Kostiantynivka is an ongoing military engagement between Russian and Ukrainian forces for control of the city in Donetsk Oblast. Following the Russian capture of Toretsk in August 2025, assaults intensified towards Kostiantynivka. Russian forces began infiltrating the city from the southeast in late October 2025, with Ukrainian units attempting to thwart these advances. By early November, the city's remaining population was estimated at 4,800. Throughout late 2025 and early 2026, Russian troops made further advances, seizing nearby villages and pushing into various parts of Kostiantynivka. Claims of control varied significantly between Russian military statements and ISW assessments. Ukrainian forces have focused on protecting resupply routes with measures like anti-drone nets. Recent developments indicate Russian forces have gained full control of the Kleban-Byk Reservoir and caused flooding by striking a dam, impacting a key road.