From buffer zone to new front: Russia pushes deeper into Sumy Oblast

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12 hours ago

In March 2025, as Ukrainian forces made their final retreat from Sudzha in Russia's Kursk Oblast, new grey spots began to appear on open-source maps on the other side of the state border, in Ukraine's Sumy Oblast.
For the first time since 2022, when Moscow's forces retreated frantically from northern Ukraine, Russian troops have once again set their sights on Sumy Oblast.
But for months, as Kyiv continued to claim hold of a thin sliver of Kursk Oblast and Russia's spring offensive escalated in eastern Ukraine, the fighting around the border in Sumy Oblast was often overlooked.
Over June, Russian gains in Sumy Oblast have sped up significantly, taking several villages and coming within 20 kilometers of the regional capital of Sumy, according to territorial changes reported by open-source mapping project DeepState.
As of June 12, fighting has been reported to have begun for the village of Yunakivka, a key stop on the cross-border highway between Sudzha and Sumy and a staging point for Ukraine's incursion into Kursk Oblast.
Over spring and summer, this part of the front line has been subject to strict restrictions on media access, with journalists barred from working with the military north of Sumy.
On June 12, President Volodymyr Zelensky said that Ukrainian forces had managed to 'push the enemy back' in some parts of Sumy Oblast, but these territorial changes are so far impossible to verify.
Speaking to journalists on June 13, Zelensky said that the Russian advance on Sumy Oblast 'had been stopped' no deeper than seven kilometers inside the Ukrainian border, adding that some ground had been regained around the village of Andriivka.
With Russia now holding over 200 square kilometers in Sumy Oblast, similar to that seized in the cross-border offensive on Kharkiv Oblast in May 2024, evaluations of the operation are torn between it being a limited escalation of fighting in the border zone or a major new Russian push.
Not long after launching the Kursk incursion last summer, Kyiv claimed that part of the offensive's aim was to create a 'buffer zone' to protect Sumy Oblast, although in reality, the spike in Ukrainian military activity saw increased Russian strikes on border settlements where Ukrainian troops and equipment were based.
After returning from a visit to Kursk Oblast in May, Russian President Vladimir Putin announced the creation of a 'security buffer zone' of his own along Ukraine's northern state border.
The sentiment was repeated on June 11 by Alexei Zhuravlev, first deputy head of the Russian State Duma's defense committee, adding that Russia was not looking to take all of Sumy Oblast (which is not one of the five regions illegally claimed by Moscow).
'A buffer zone of one hundred kilometers along the Russian border will be enough,' Zhuravlev said. 'Let them evacuate, retreat in fear, waiting everywhere for the attack of the Russian army.'
Even if Moscow wanted to, mounting a direct assault on a large city like Sumy – with a pre-war population of 255,000 – would almost certainly be out of the reach of Russia's capabilities for the moment, said analyst Emil Kastehelmi, a member of the Finland-based open-source intelligence collective Black Bird Group.
'The Russians haven't been able to actually capture any larger cities in Ukraine since 2022 (with the surrounding and capture of Mariupol in Donetsk Oblast),' he said.
'What they can do is put heavy pressure on the Sumy direction and try to gain as much land as possible, in order to bring Sumy into range of artillery and drones, tying Ukrainian troops into defensive battles and giving Russia some leverage in upcoming negotiations.'
Russia's push in Sumy Oblast comes amid a broader spring-summer offensive that has also seen significant gains in Donetsk Oblast, especially on either flank of the embattled city of Pokrovsk.
With the Ukrainian army significantly overstretched along hundreds of kilometers of front line and suffering from chronic manpower shortages, especially in the infantry, Russia's pressure on Sumy Oblast creates more dilemmas.
'The Russians are most likely trying to create as many issues for the Ukrainians as possible in several directions simultaneously,' Kastehelmi said.
'They aim to create a cascading situation where the Ukrainians need to answer to a crisis in a certain sector by throwing in units from another place, resulting in units not being able to do proper rotations.'
Still, with Russian forces relying on the same formula of creeping, infantry-based assaults employed all across a drone-saturated front line, maintaining pressure also comes with sacrifices made in offensive potential elsewhere.
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Speaking to the Kyiv Independent, Volodymyr Martyniak, a company commander in the 22nd Special Purpose Battalion of Ukraine's 1st Presidential Brigade, said that Russia's main advantage in Sumy Oblast remained their ability to send wave after wave of lightly-mounted infantry at the Ukrainian defense.
'They are being organized into ultra-minimal teams, of just a couple of people, using the bare minimum of equipment,' he said,' things like quad bikes, other motorized vehicles, motorcycles to move quickly through rough terrain.'
According to Martyniak, Russian forces in the area use a mix of expendable, cannon-fodder style infantry troops in the first waves of an attack, which are then followed by more experienced soldiers, demonstrating tactics refined since the Battle of Bakhmut over two years ago.
'At first, soldiers go in simply to move forward and dig in,' he described. 'Then, once enough of them have gathered in a certain area, enough to justify bringing in something more serious, a more advanced, better-trained, and correspondingly more professional unit follows.'
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Just as when Russian troops broke across the border toward Kharkiv last May, the current advance in Sumy has raised concerns among the military and society about the preparedness of Ukrainian fortifications along the state border.
As per the Defense Ministry's fortification-building initiative laid out in late 2023 and executed over 2024, while Ukrainian brigades and combat engineers would build the two lines of defense closest to the enemy, the third and strongest line of defense would be built by civilian contractors coordinated and paid for by regional administrations.
Rather than coherent lines of defense, these fortifications were built around platoon strongpoints — individual fortresses consisting of several reinforced concrete bunkers connected by trenches.
But as in Kharkiv and Donetsk oblasts, these fortifications have been criticized as poorly designed and built. Trenches and platoon strongpoints planned in 2024 were often constructed in open fields, with little regard for concealment or protection from drones.
One Ukrainian combat medic, who requested to remain anonymous for security reasons, said that compared to areas in Donetsk Oblast where fortifications had been built in advance even if not ideally, nothing of the like could be seen in Sumy Oblast.Although defending Ukrainian territory was easier than holding positions across the border because of better logistics routes, he said, there were still little to no prepared lines of defense waiting for them after the withdrawal.
Ultimately, the strength of any line of defense is dependent not only on the fortifications themselves, but on the ability of the defending side to man them with enough combat effective infantry.
Excess losses among Ukrainian units holding Kursk Oblast, where Ukrainian commanders had reported politically-motivated orders to hold Russian territory despite logistics routes being controlled by Russian drones, have made it easier for Russian forces to continue their advance across the border.
In these conditions, Martyniak — whose battalion fought inside Kursk Oblast before crossing the border — says the defense of territory inside Ukraine started straight after the withdrawal from Sudzha in March.
According to the commander, Ukraine's main problem in defense consistently remains the lack of manpower in the infantry.
Efforts have been made to improve training and focus more on replenishing existing brigades rather than creating new ones, but by 2025, almost all new Ukrainian infantrymen are mobilized rather than volunteer soldiers.Meanwhile, as the skies above the front line become more saturated with enemy drones with each passing month, the experience of the foot soldier only gets deadlier and more difficult.
'Replenishments come in, but they must be trained, they must be professional, and, let's say, they must have some kind of motivation,' Martyniak said.
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Further Russian gains toward Sumy could gradually bring the city into range of enemy first-person view (FPV) drones, which Russian forces often use not only to cut off enemy logistics, but to make entire cities unlivable by targeting civilian vehicles, as has been done with Kherson in the south.
With Russian forces constantly improving the range of their FPV drones, including those running on unjammable fiber optic connections, the first such drones could fly into Sumy sooner rather than later.Recent strikes increasingly deep behind Ukrainian lines in Donetsk Oblast including on the cities of Sloviansk and Druzhkivka have shown how FPV drones can fly further and further into the Ukrainian rear even if the front line itself doesn't move much.
Over 2025, amid Sumy's increasing proximity to the front line and continued intense fighting along the border has seen the city subject to strikes from other weapons, including a missile strike in April that killed 35 people and wounded 129.
On June 4, Russia struck Sumy with multiple-launch rocket systems, killing four and wounding 28, in the first attack with this kind of weapon recorded on the city since it was almost surrounded by Russian forces at the onset of the full-scale invasion in 2022.
As the summer campaign in Ukraine heats up, Sumy Oblast threatens to become a new regular hotspot along the front line, whether or not Russian forces can keep up their pace of attack.
'Their real advantage here is that they have a massive military resource, first and foremost — a very large one,' said Martyniak, 'the enemy, as always, is building up its forces; they don't stand still, things are always in motion on their side, and they're constantly coming up with something new.'
'We, for our part, also try to respond with the same skills, the same experience, the same capability; we are carrying out our missions and holding the line with dignity.'
Hi, this is Francis Farrell, and thank you for reading this article. When thinking about a major new front opening in Sumy Oblast, I can only hope that Zelensky is right when he says that Russia's advance has been stopped, and that just like with Kharkiv Oblast last year, the lines will stabilize and no more red will appear on the map in the area. Hope is nice, but whatever happens Russia only stops if they are stopped, and that comes at a price. For that reason, we will not stop what we are doing for a minute.
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