Ukraine’s remaining fortified belt in Donetsk Oblast — centered on Sloviansk, Kramatorsk, Druzhkivka, and Kostiantynivka — has become one of the war’s most important defensive lines, and one of Russia’s hardest targets to crack. According to the Institute for the Study of War, Russian officials continue to frame the capture of all of Donetsk as achievable in the near term, but ISW analysts say the remaining fortified area is likely to hold far longer than Moscow claims, with full seizure of the region unlikely before 2027 or 2028 under current conditions.
The four cities sit along a roughly 50-kilometer north-to-south defensive corridor tied to the H-20 highway, a route that links key logistics and military movement across eastern Ukraine. Sloviansk and Kramatorsk form the northern half of the line and serve as major logistics hubs, while Druzhkivka and Kostiantynivka anchor the southern sector. Together, the cities and surrounding settlements have been heavily fortified over more than a decade, giving Ukraine a layered defensive network that is far more difficult to penetrate than open terrain farther west.
Why These Cities Matter
The significance of Sloviansk, Kramatorsk, Druzhkivka, and Kostiantynivka is both military and symbolic. Militarily, they function as supply, command, and staging centers for Ukraine’s eastern front, helping sustain forces across Donetsk Oblast. Politically and strategically, losing them would push the front line westward and place Russian forces on terrain that ISW describes as less defensible for Ukraine than the current positions.
Kramatorsk also stands out as a key administrative center after the loss of Donetsk city to Russian occupation, making it especially important as a hub for governance and wartime logistics. Kostiantynivka has increasingly come under pressure as Russian forces seek to shape the battlefield ahead of wider assaults on the fortress belt. ISW says Russia’s campaign has so far depended on slow advances, drone pressure, and efforts to isolate Ukrainian positions rather than rapid breakthroughs.
Terrain And Defense
Terrain is one of the biggest reasons this area remains so important. ISW says the fortress belt is “optimized for defense,” while the land farther west is comparatively poor defensive terrain, with more open fields and fewer natural barriers. That means if Ukraine were forced back from this line, the next defensive positions would likely be harder to hold and more expensive to fortify.
The current line benefits from urban density, existing fortifications, and the concentration of roads and infrastructure that Ukraine has spent years reinforcing. In contrast, the western approach offers fewer natural advantages and would require major new defensive construction. In practical terms, this makes the four-city belt not just a battlefield objective, but a key barrier slowing any further Russian push deeper into central Ukraine.
Battlefield Outlook
ISW analysts told RBC-Ukraine that Russia is still likely to face a prolonged fight for the fortress belt, even if it continues to gain ground elsewhere. They assessed that the capture of the remaining Donetsk-held areas, including these fortified cities, would require time, resources, and sustained pressure that could extend into 2027 or 2028. The analysts also noted that Russian forces have not shown the ability to rapidly seize large urban centers like Sloviansk and Kramatorsk since 2022.
For now, the four cities remain a defining test of Ukraine’s eastern defense and Russia’s ability to convert battlefield momentum into operational success. Their fate may shape not only the next phase of the war in Donetsk, but also the broader stability of Ukraine’s southeastern front.
