Russia launches advance on Sumy Oblast to build buffer zone and pressure the city — ISW

The enemy have made minor advances near the border between Ukraine’s Sumy Oblast and Russia’s Kursk Oblast. However, the Russian grouping in this area is unlikely to be capable of launching a full-scale offensive on the city of Sumy anytime soon without substantial reinforcements, ISW analysts said.

Responding to Ukrainian Armed Forces Commander-in-Chief Oleksandr Syrskyi’s remarks about intensifying Russian operations “on all key fronts” — including the start of offensive actions in Sumy and Kharkiv Oblasts — ISW described Russian advances near the Vovodymyrivka–Zhuravka–Novenke line (north and northeast of Sumy) as “gradual but steady.”

In addition to mounting pressure in northern Sumy Oblast, Russia is reportedly trying to push Ukrainian troops out of their remaining positions in Kursk Oblast. Analysts noted that Ukrainian forces withdrew from the town of Sudzha and much of Kursk Oblast in mid-March 2025, but progress has since slowed. Over the past month, Russian forces have shifted their focus to northern Sumy.

Ukrainian military observer Kostiantyn Mashovets estimated on April 9 that around 62,000 to 65,000 Russian soldiers and border guards are operating in Kursk Oblast. In January 2025, Syrskyi reported that approximately 67,000 Russian troops and 11,000 North Korean personnel were deployed in Oblast. ISW added that Russian forces likely suffered some losses in the heavy attacks in March and early April.

Russian marines from the 155th Brigade were reportedly redeployed from Kursk to Belgorod to respond to Ukrainian attacks in that area — another indicator that Moscow may not be amassing forces in Kursk for a large-scale Sumy offensive. Instead, this suggests Russian commanders believe they can achieve operational objectives using the existing grouping, ISW said.

Russia is likely attempting to create a limited, defensible buffer zone along the international border in Sumy Oblast. Analysts do not rule out a future offensive deeper into Sumy — particularly toward the city itself — but for now, Moscow appears focused on positioning artillery close enough to place it under threat.

ISW noted that recent Russian attacks in northern Sumy could signal an effort to capitalize on Ukraine’s withdrawal from Kursk by either building a buffer zone or laying the groundwork for a push toward Sumy. On March 12, in his visit to a Russian command post in Kursk, Russian dictator Vladimir Putin ordered General Staff Chief Valery Gerasimov to “consider establishing a security zone” along the border. Foreign Minister Sergey Lavrov made similar comments in 2024 regarding Kharkiv Oblast, citing a supposed need for a buffer zone.

Putin may now seek to expand his territorial claims by using the threat to Sumy as leverage. ISW noted that Moscow was already demanding that Ukraine cede not only temporarily occupied territories in Donetsk, Zaporizhzhya, and Kherson oblasts, but also areas now under Ukrainian control — namely, citites of Mykolaiv and Kharkiv. Pressuring Sumy could become part of this broader claim.

Still, analysts believe the Russian force in Kursk lacks the capacity to capture a major city like Sumy after months of intense fighting — unless reinforced from other areas. That, in turn, would require Russia to scale back operations elsewhere, making those fronts more vulnerable to Ukrainian advances — an unlikely move at this stage.

Therefore, ISW assessed that Russian forces are more likely trying to carve out a limited and defensible buffer zone in northern Sumy Oblast and to position artillery to pressure the city. 

Moscow may then shift its forces to support offensives elsewhere in Ukraine. While threatening Sumy may yield political and psychological pressure, analysts suggest it remains more valuable as a tool for coercion than as a feasible objective for capture.