Ukraine’s Operation Vivaldi has disrupted Russian advances in northern Donetsk Oblast, with Ukrainian forces recapturing 125–176 square kilometers around Lyman since mid-September and collapsing a planned pincer movement toward the Sloviansk-Kramatorsk defensive belt. Russian net territorial gains turned negative in September according to open-source assessments, as units shifted to defensive positions amid higher casualties and logistical strain. Moscow retains localized pressure near Kostiantynivka and Dobropillia but has struggled to sustain momentum toward remaining Ukrainian-held areas in Donetsk. Putin has stated confidence in securing the full region by year-end, though independent analyses indicate the current pace of advance makes that timeline improbable without major shifts in manpower, air support, or external developments. Winter weather and Ukrainian defensive reinforcements remain key variables for frontline dynamics through late 2026.