- Russian infiltrators may have marched into the westernmost districts of Kostiantynivka in eastern Ukraine's Donetsk Oblast
- Hard evidence is scarce, but observers warn that Russian gains in Kostiantynivka may be going unreported
- If enough Russian infantry accumulate, they could sever the supply line into Kostiantynivka and trigger the eventual collapse of the Ukrainian defense
The Russian Center Group of Forces is trying to do in Kostiantynivka what it recently did in neighboring Myrnohrad and Pokrovsk: infiltrate the front-line city with small groups of infantry and sow chaos among the Ukrainian defenders until enough Russians can accumulate to force the Ukrainians out.
Mapper Playfra was the first to report the presence of Russian infiltrators in the Berestovyi district on the western edge of Kostiantynivka. "It is unclear if they were subsequently eliminated or not, but the fact that they were present there clearly hints at Russian intentions in this sector," Playfra wrote on Tuesday.
Previously, the Russians had tried to penetrate into Kostiantynivka along its eastern edge around Santurynivka district, but a stiff Ukrainian defense repulsed the Russian assaults. So the Russians pivoted west in recent days. "They're attempting to find another way into the city," Playfra reported.
And they may be succeeding. "This side was evidently less manned and controlled by Ukrainian forces," Playfra explained. If the Russians can seize and hold positions in Berestoviy district and accumulate reinforcements, they could come "closer to an encirclement of Kostiantynivka," Playfra wrote.
It's important to note that Playfra, while usually accurate owing to their sources on the ground in Ukraine, is so far the only mapper to observe Russians in Berestovyi district.
But another observer warned Playfra is, if anything, being too conservative in his assessment of Russian progress in Kostiantynivka. "I believe that the Ukrainian situation in ... the southwest outskirts of Kostiantynivka may be much worse than colleague Playfra presents it on his map," Thorkill wrote.
"Analysis of available geolocations and scraps of other information indicates that since October 2025, Russians have been conducting offensive operations there—with short operational pauses," Thorkill added.
The Russians' aim, Thorkill concluded, is to penetrate far enough north to sever the H-20 road—the main supply line for the Ukrainian garrison in Kostiantynivka, which includes the 36th Marine Brigade, parts of the 28th and 100th Air Assault Brigades, and the 107th, 109th, and 122nd Territorial Defense Brigades.
"Overall," Thorkill warned, "we're dealing with a repeat of a similar Russian infiltration operation from Pokrovsk from the summer/fall of 2025."
Faltering defense
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Pokrovsk, Myrnohrad, and Kostiantynivka once represented a nearly contiguous, 50-km defensive line for Ukrainian forces in eastern Ukraine's Donetsk Oblast. But the Russian Center Group of Forces reached the outskirts of Pokrovsk in late 2024 after a long bloody march from the ruins of Avdiivka.
A lengthy siege ensued. It took a year, but with patience, persistence—and, yes, heavy losses—the Russians infiltrated, destabilized, and eventually captured most of Pokrovsk in late November and most of Myrnohrad a few weeks later.
The Russians achieved these victories without committing significant numbers of armored vehicles. Instead, they mostly sent in infantry, just a few at a time, hoping that a small number of troops on foot would better evade Ukraine's drones.
It worked—but only because Ukrainian brigades in Pokrovsk and Myrnohrad lacked the manpower to counterattack the Russian infiltrators and eject them from their new positions inside the settlements. The same manpower shortage may doom the Ukrainian defense of Kostiantynivka, too.
That's because the government in Kyiv still hasn't figured out how to recruit or mobilize enough fresh troops to make good front-line losses. "Whether Ukraine can stabilize the manpower situation in its brigades holding the front is likely the most important single factor that will determine how far Russia will advance in 2026," wrote Rob Lee, an analyst with the Foreign Policy Research Institute in Philadelphia.
Can Kyiv fix its manpower problem in time to save Kostiantynivka?
