Surrender of Donbas to force Ukraine to lose strategic 'fortress belt' that held back Russia for 11 years — ISW
The surrender of the remaining territories of Donetsk region within the framework of ceasefire negotiations will force Ukraine to abandon the so-called "fortress belt," the main fortified line of defense that has held back Russia's territorial ambitions for 11 years, experts from the Institute for the Study of War (ISW) believe.
The fortress belt includes key towns — Sloviansk, Kramatorsk, Druzhkivka, Oleksiyevo-Druzhkivka and Kostiantynivka, which have remained under the control of Ukrainian troops since 2014 and are of significant strategic importance as logistical and administrative centers. The length of the defense line reaches about 50 kilometers.
"Ukraine's fortress belt has served as a major obstacle to the Kremlin's territorial ambitions in Ukraine over the last 11 years," the ISW report of August 8 reads.
Ukrainian forces have held this defense line since 2014, after it was liberated from pro-Russian forces. Attempts by Russian troops to capture Sloviansk and the cities of the fortress strip in 2022-2023 were unsuccessful, and counteroffensives by the Armed Forces of Ukraine drove the enemy far from key positions.
In the event of the surrender of these territories, Ukrainian troops will lose a strategically important defense strip with no guarantees of lasting peace, which could give Russian forces an advantage in resuming the offensive.
Russian troops have now intensified attempts to capture the so-called "fortress belt" from the southwest, concentrating forces in Toretsk and eastern Pokrovsk directions. According to the Institute for the Study of War (ISW), units of the 20th and 150th Motorized Rifle Divisions from the Kurakhove direction were transferred to the area in February 2025. In May, they were joined by elements of the 39th Motorized Rifle Brigade, indicating an increase in the offensive efforts of Russian troops in these directions.
"Russian forces failed to conduct a wide envelopment of Ukraine's fortress belt in 2022, and such an operation three and a half years into the war would likely be a multi-year effort with significant personnel and materiel losses," the report reads.