Chapter 1
The Fortress Belt is the chain of Donetsk cities Ukraine still holds…
The Fortress Belt is the chain of Donetsk cities Ukraine still holds: Slovyansk and Kramatorsk at its anchor, Druzhkivka and Kostiantynivka to the south. As the Institute for the Study of War reconstructs it, Russia built its 2026 campaign for Donetsk around them as a wide encirclement — one arm north through Lyman and Svyatohirsk, another north from Dobropillya, meeting near Barvinkove — while attacking Kostiantynivka head-on. By mid-October the northern arm had collapsed, the southern arm was still pressing, and no city in the belt had fallen. Throughout, both sides’ accounts have run well ahead of what geolocated evidence shows, so what is confirmed and what is merely claimed is a large part of the story.
Chapter 2
Through the summer Russia tried to wear the belt down from the south…
Through the summer Russia tried to wear the belt down from the south and the air. In late July it pushed toward Dobropillya, though ISW recorded no confirmed advance there. In Kostiantynivka, which Moscow claimed captured on 5 July, ISW held that infiltration was not control; by 28 July geolocated footage put Russian troops in the west of the city, and ISW named the method — glide bombs, then infantry — that had taken Avdiivka, Vuhledar, Kurakhove and Toretsk before it. In early August ISW assessed that Russia had opened a glide-bomb campaign to cut the belt’s logistics, striking a bridge in eastern Slovyansk, a shaping effort it judged unlikely to bring quick gains. By 26 August Ukraine had pulled its main force in Kostiantynivka back across the Kryvyi Torets river to hold the north and north-west, and Russian rocket launchers had joined the glide bombs over Slovyansk.
Chapter 3
Russia then opened a new approach from the east
Russia then opened a new approach from the east. On 23 August ISW assessed Russian advances on the southern bank of the Siverskyi Donets toward Pyskunivka, bypassing Lyman. The claims ran further: on 27 August Russia’s chief of general staff, Valery Gerasimov, said his forces stood four kilometres from Slovyansk and had seized more than 100 square kilometres around Druzhkivka alone; ISW found no Russian presence in the villages he named, put his forces about 14 kilometres from the city, and measured 52 square kilometres seized across all of Donetsk in those two months. Slovyansk’s own military administration said on 1 September that Russian forces were seven to ten kilometres away and shelling the city with artillery. A Ukrainian brigade spokesman said foreign recruits made up about a third of the Russian force massing for Lyman.
Chapter 4
The northern arm broke at Lyman
The northern arm broke at Lyman. From late August Ukrainian troops cleared Russian infiltrators from villages north-west of the town and began cutting off the Russian salient there. On 15 September Ukraine’s 3rd Army Corps named the operation Vivaldi. Its own totals have run ahead of what others confirm — 176 square kilometres after three phases, where ISW assessed at least 147, and 277 square kilometres and 16 settlements after four, which no tracker has confirmed — but the direction is not in dispute. On 8 October ISW concluded in a special report that Ukraine had defeated Russia’s 2026 campaign for Donetsk, while cautioning that this was no Kharkiv-scale rout. Russia had seized about 630 square kilometres of the oblast in the year to 1 October and had 5,382 left to take; Putin has reportedly moved his deadline for the whole of Donetsk from the end of 2026 to spring 2027, and ISW has forecast that Russia will miss it. Russian military bloggers have since conceded ground east of Slovyansk.
Chapter 5
What remains is the southern half of the contest
What remains is the southern half of the contest. Russia is pressing Dobropillya before winter, which ISW calls critical to what is left of the encirclement. In Kostiantynivka Moscow has twice announced a capture that ISW does not see: by its count Russian forces had advanced into about 38 percent of the town by 6 October, and Russia is planning its move on Druzhkivka as if Kostiantynivka were already held. A new Russian drone regiment has been reported in the Lyman direction but not located, and ISW judges the two Russian armies around Lyman badly degraded. The open questions are whether the southern arm and the frontal assault can do what the northern arm could not, and whether Kostiantynivka holds.
And now
Russia’s commanders claim the Fortress Belt’s southern cities; the evidence does not show them taken.
On October 16 Russia’s chief of general staff, Valery Gerasimov, told Putin his forces had captured Dobropillya, Kostiantynivka and Oleksiievo-Druzhkivka, entered Druzhkivka and reached the outskirts of Kramatorsk. ISW calls the claims false. It sees only limited infiltration in Dobropillya and puts Russian troops, infiltrators included, at least 9 kilometres from Kramatorsk and 12 from Druzhkivka. Ukraine’s General Staff and the Azov corps say Dobropillya and the villages around it remain Ukrainian, and a Russian military blogger conceded that no advance into the town’s centre is confirmed. DeepState does show a small Russian advance near Svitle, beside it.
Kostiantynivka is where the fighting is real. Russian troops have infiltrated much of its south and centre without consolidating them, and are now working north of the city around Novodmytrivka and Molocharka, on an observer’s account ISW accepts. Ukrainian troops still hold positions inside it.
In the north, the Russian salient at Lyman stays collapsed after Operation Vivaldi, and ISW assesses that Ukrainian forces held or advanced east of Slovyansk and Kramatorsk.
Where it stands today →