Kursk

Kursk Oblast became the first Russian territory held by a foreign army since World War Two when Ukrainian forces launched a cross-border incursion in August 2024. Ukraine seized an estimated 1,200-1,300 km² at the operation's peak, establishing a foothold that it held for several months before Russian and North Korean forces pushed back. The Kursk operation forced Russia to divert frontline units from the Donetsk axis and signalled that the conflict was not confined to Ukrainian territory.

The oblast sits in Russia's south-western Central Federal District, bordering Sumy Oblast in Ukraine to the south and Belgorod Oblast to the east. It is predominantly agricultural with a population of roughly 1.1 million and hosts one of Russia's major nuclear power plants. General Gerasimov cited protecting Kursk and Belgorod from Ukrainian cross-border raids as the explicit rationale for Russia's March 2026 buffer-zone push into Ukrainian Sumy Oblast.

By late May 2026, the Kursk incursion had become the standard benchmark against which Russian territorial performance is measured. ISW assessed on 3 May that Russia suffered its first net territorial loss since the Kursk incursion, with April 2026 gains of only 116 km² net. In the four weeks from 28 April to 26 May 2026, Russia net-lost 100 square miles (260 km²) of Ukrainian territory, its worst four-week result of the war, putting Russia's territorial position at its weakest since the Kursk incursion of August 2024 when Ukraine seized roughly 100 sq miles in four weeks. The parallel is explicit: both represent periods when Russia's net advance rate inverted from gain to loss.