Russian forces face years of grueling battles to seize Donbas

ISW analysts drew attention to the Ukrainian Air Assault Forces' report on the liberation of the village of Berezove in Dnipropetrovsk Oblast (southeast of Oleksandrivka), explaining that this allowed the Defense Forces to eliminate a Russian "salient" in this sector.

Experts wrote that since late January 2026, Ukrainian Defense Forces have achieved significant tactical successes in the south and regained more territory than Russian forces captured in February 2026.

Amid statements by the Ukrainian side about the clearing and liberation of over 400 square kilometers in the Oleksandrivka and Hulyaipole directions, ISW verified the liberation of at least 334.06 square kilometers in southern Ukraine since Jan. 1, 2026. At the same time, analysts emphasize that the ISW's conservative mapping methodology likely underestimates Ukrainian gains.

The Institute for the Study of War forecasts that the invaders are unlikely to capture the Ukrainian belt of "fortress" cities in Donetsk Oblast in 2026. Analysts recalled that this refers to the four largest and best-fortified major cities in Donetsk Oblast [Kostyantynivka, Druzhkivka, Slovyansk, Kramatorsk — ed.], with a combined pre-war population of over 380,000, stretching from north to south along the H-20 Kostyantynivka-Slovyansk highway. Russian troops tried but failed to capture this chain of cities in 2014 and 2022. Therefore, this operation in the fifth year of the full-scale invasion will likely take the form of a multi-year effort with significant losses of personnel and equipment.

ISW experts provided a time-stamped map demonstrating the slow pace of the Russian advance toward Kostyantynivka.

ISW believes that Russian troops have already begun their 2026 spring-summer offensive against the fortress city belt, noting a significant increase in mechanized and motorized assaults across various sectors of the front between March 17 and March 21. Experts also recorded an intensification of Russian strikes and the movement of heavy equipment and troops on the front lines.

At the same time, as the Institute for the Study of War notes, Russian troops have not yet demonstrated the ability to quickly bypass, break through, or otherwise capture cities the size of those in the Donbas fortress belt. Thus, it took the occupiers nearly two years to capture Pokrovsk — a much smaller city with a pre-war population of 60,000, analysts highlighted.

Within Russia's domestic information space, Russian officials are already predicting the occupation army's slow advance and high casualties, ISW stated. Russian State Duma Defense Committee Chair Andrei Kartapolov stated on March 26 that it is too early for Russia to speak of a "triumphant spring offensive." Kartapolov noted that the battles on the front are difficult, specifically pointing out that fighting in Kostyantynivka [Russian offensive actions — ed.] is complicated by the city's size and Ukraine's defensive fortifications.

The Kremlin clearly realizes that the capture of the Donbas fortress belt by Russian troops is not inevitable, which is why it demands that Ukraine surrender the unoccupied parts of Donetsk Oblast without a fight, ISW experts believe. In their view, the Kremlin seeks to achieve this concession to preserve human and material resources for Russia and secure a more advantageous position for a potential reinvasion in the future.