Ukraine’s Operation Vivaldi Foils Russian Plan to Encircle Donetsk, ISW Reports
A counter-offensive by Ukrainian forces on the Lyman axis, known as Operation Vivaldi, has successfully collapsed the northern arm of a Russian pincer movement, according to an assessment by the Washington-based Institute for the Study of War (ISW). The Russian operation had aimed to encircle and occupy the remaining Ukrainian-controlled territory of the Donetsk region.
The ISW report, based primarily on open-source intelligence, detailed that the Russian campaign focused on a deep pincer movement targeting the "fortress belt"—a defensive and logistical network protecting the Ukrainian-held portion of the Donbas. The plan involved advancing from Lyman in the north and Dobropillia in the south-west, with the two arms intended to link up near Barvinkove in the Kharkiv region.
Dismantling the Northern Pincer
Operation Vivaldi dismantled the northern arm of this planned encirclement. Ukrainian forces advanced along the Ridkodub–Nove–Novomykhailivka line in the north and the Yarova–Drobysheve–Stavky line in the south. This advance collapsed the salient Russia had established to threaten Sloviansk from the north-east, forcing Russian units onto the defensive.
According to Andrii Biletskyi, the commander of Ukraine’s 3rd Army Corps, the first three phases of the operation in mid- to late September liberated 176 square kilometres of territory. Meanwhile, Ukrainian President Volodymyr Zelenskyy stated that between 125 and 140 square kilometres had been liberated as of October 3, adding that Russian losses had risen sharply over the preceding two to three months. The ISW suggested that the operation may have been even more successful than Kyiv’s official figures indicate.
The defeat of the northern pincer has forced Russia to abandon its plans to advance on Sloviansk from the north-east. It also deprived Russian forces of positions intended to threaten the northern approaches to the fortress belt. By retaining control over the Lyman area, Ukraine preserved key supply routes, while Russian units on other parts of the front may have been redeployed to reinforce the northern sector.
Impact on Russian Strategy
With the northern arm collapsed, Russia’s south-western advance from the Pokrovsk–Dobropillia area now faces far more ambitious objectives on its own. The ISW regards the collapse of the northern pincer as an operational failure for Moscow, as it lost both ground around Lyman and a key component of its campaign plan for the fortress belt.
While Russian forces retain limited gains around Kostyantynivka and east of Sloviansk, they have struggled to sustain their pace of advance. The ISW noted that Russia's reliance on infantry infiltration, drones, and bombardment can produce gradual attrition but cannot generate the fast mechanised manoeuvres required to collapse Ukraine’s defences at the scale Moscow needs.
Although the situation remains fluid and Russian forces will probably adapt over time, the ISW concluded that Ukraine has temporarily halted the advance. While further Russian mobilisation and technological adaptation could alter the balance, the think tank noted that neither would necessarily enable a breakthrough.
Disputed Territorial Claims
The ISW also challenged claims widely circulated in pro-government Russian media that Russian forces had occupied an additional 1,301 square kilometres of Ukrainian territory in September alone. Using geolocated photo and video footage, satellite imagery, and visually confirmed data, the institute calculated that Russian assault units were actually pushed out of at least 80 square kilometres during that month.
According to the ISW, Russia's net retreat in September rose to 175.18 square kilometres, which includes areas it temporarily penetrated but failed to hold.
Furthermore, the think tank disputed Russian President Vladimir Putin’s recent statement to the Valdai Club that Russia occupies 89 percent of the Donetsk region. The ISW assessed that Russian-occupied territory in the region stands at no more than 81 percent. The institute described Putin’s claims of September breakthroughs as being "so far removed from reality that they resemble hallucinations," attributing the discrepancy to a deeply embedded culture of dishonesty within the Russian military command.
