Full Breakdown
Operation Vivaldi Halts Russia’s Encirclement Attempt
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Background and Strategic Objectives
In September 2026 the Russian military launched a deep-pincer offensive aimed at the “fortress belt” that protects the Ukrainian-held part of the Donetsk region. The northern arm advanced from Lyman, while the southern arm moved from the Pokrovsk–Dobropillia axis, with the two forces intended to link near Barvinkove in Kharkiv oblast. Success would have brought most of Donetsk under Moscow’s control, a long-standing objective of the Kremlin.
Territorial Shifts and Quantitative Assessment
The Institute for the Study of War (ISW) assessed that Ukraine’s counter-offensive, dubbed Operation Vivaldi, dismantled the northern pincer. Ukrainian troops progressed along the Ridkodub-Nove-Novomykhailivka line in the north and the Yarova-Drobysheve-Stavky line in the south, collapsing the salient that threatened Sloviansk from the north-east. ISW calculated that Russian assault units were pushed out of at least 80 sq km in September and that the net Russian retreat that month amounted to 175.18 sq km, including areas briefly penetrated but not held.
Commander Andrii Biletskyi of Ukraine’s 3rd Army Corps reported that the first three phases of the operation, conducted in mid- to late September, liberated 176 sq km. President Volodymyr Zelenskyy later gave a lower estimate of 125-140 sq km as of 3 October, noting a sharp rise in Russian losses over the preceding two to three months.
Russia retained limited gains around Kostyantynivka and east of Sloviansk but struggled to sustain its advance. ISW attributes this to Russian reliance on infantry infiltration, drones and bombardment, which cannot achieve the rapid mechanised manoeuvres required for a breakthrough.
Official Statements and Divergent Claims
President Zelenskyy emphasized the reclaimed territory and the sharp increase in Russian casualties. Russian President Vladimir Putin, speaking to the Valdai Club, claimed that Russia now occupies 89 % of Donetsk region. ISW disputes this, estimating Russian-occupied territory at no more than 81 %.
Implications for the Donbas Front
By halting the northern arm of the encirclement, Ukraine preserved key supply routes around Lyman and prevented Russia from threatening the northern approaches to the fortress belt. The setback forces Moscow to redeploy units to reinforce the northern sector and leaves the southern advance facing more ambitious objectives without the support of a coordinated pincer. While ISW warns that further Russian mobilisation and technological adaptation could alter the balance, the current assessment indicates that Ukraine has, for now, stopped the Russian push toward full control of Donetsk.