Ukrainian forces claimed a significant battlefield victory in mid-December 2025 when the Third Army Corps, working with military intelligence units, announced they had destroyed an entire Russian regiment near Lyman in Donetsk Oblast. The operation marked one of the war’s largest single tactical successes in months, with commanders reporting the regiment left combat-ineffective and Ukrainian positions substantially improved in the heavily contested forest sector.
A Coordinated Assault Breaks Russian Lines
On December 18, 2025, Ukrainian military officials disclosed that their forces had launched a joint operation in the Serebianskyi Forest, a dense woodland east of Lyman that has witnessed relentless fighting since 2022. The Third Army Corps and the Defence Intelligence of Ukraine coordinated the strike, which Ukrainian sources say eliminated a Russian regiment estimated to comprise roughly 2,000 troops on paper. General Andriy Biletsky, commander of the Third Army Corps, stated that “together with the HUR, we achieved an operational-tactical result in the Lyman direction,” emphasizing the partnership between regular army units and intelligence operatives.
The operation also resulted in the capture of an undisclosed number of Russian soldiers, adding to the psychological impact of the offensive. Ukrainian outlets released footage showing participation by the 3rd Reconnaissance Battalion, the 2nd Mechanized Battalion of the 3rd Assault Brigade, the Fatum unmanned systems unit of the 60th Mechanized Brigade, and the intelligence agency’s Artan special forces.
Front Line Straightened and Positions Improved
Ukrainian commanders framed the operation as more than a strike against a single enemy formation, describing it as a deliberate reshaping of the local battlefield. The Third Army Corps reported that its assault “stabilized the front line and improved tactical positioning” in the Lyman sector, effectively straightening a dangerous bulge that had left Ukrainian troops vulnerable to attack from multiple angles. In the thick Serebianskyi Forest, where tree lines conceal ambushes and drone operators dominate sight lines, this repositioning reduces the space Russian forces have to maneuver, rotate troops, or sustain offensive pressure.
The operation capped months of smaller Ukrainian strikes that gradually eroded Russian cohesion through the autumn, setting conditions for what military analysts described as a culminating blow that transformed grinding attrition into a sudden rout. By mid-December, Ukrainian forces had an opportunity to deliver a decisive strike, depriving Russia of coherent control over a key forest corridor and limiting its ability to reinforce or reposition forces quickly.
Lyman’s Strategic Weight in the Donbas Struggle
Lyman, a railway junction town of approximately 20,000 residents before the war, has shifted hands and absorbed punishment throughout the conflict. Russian forces captured it in May 2022, only to lose it that October when a Ukrainian counteroffensive in Kharkiv and Donetsk oblasts pushed them back—an operation in which Ukraine encircled an estimated 5,000 Russian troops—in what was widely recognized as a significant operational success. Since then, the neighboring Serebianskyi Forest has become a grueling close-quarters battlefield, with Russian troops sending wave after wave of mobilized soldiers into the woods. By summer and autumn 2025, Russian forces had inched the front line closer to Lyman, bringing Ukrainian positions fully into range of first-person-view drones and artillery.
The town’s defense carries outsized importance because it serves as a northern gateway to Sloviansk, one of Ukraine’s key defensive hubs in Donetsk Oblast. Against the backdrop of Russia’s expanded grouping of approximately 710,000 troops committed across the theater, as reported by Ukrainian Commander-in-Chief Oleksandr Syrskyi, Ukraine has aimed to blunt attacks in places like Lyman to prevent a cascading collapse of the front. Syrskyi told international partners in mid-December that Russia had increased its forces “to around 710,000 troops to conduct a strategic offensive operation,” underscoring the scale of pressure Ukrainian defenders face.
Questions of Verification and What Comes Next
Despite the dramatic nature of Ukraine’s claims, independent verification remains limited. Military analysts caution that organizations tracking the war typically rely on satellite imagery, geolocated videos, and corroborating reports to validate major battlefield assertions, a process that can take days or weeks. As of late December, the Institute for the Study of War had not recorded significant new Russian advances near Lyman following the reported operation, suggesting at minimum a pause or disruption in Moscow’s local offensive. On the Russian side, the fallout has fed frustration among pro-war commentators, who have complained of exhausted units and slow, costly advances around Lyman.
Reports of large groups of prisoners taken near Lyman add to the sense of strain, signaling that morale in certain units may be cracking under pressure. Ukrainian leaders are already examining how the operation’s model of integrated intelligence, drones, mechanized infantry, and special forces could be replicated elsewhere. On the ground, Ukrainian troops are working to hold and deepen their gains, improving fortifications and logistics in newly secured areas while deploying more drones to monitor any Russian attempts to regroup. The big question now is whether this blow in the Serebianskyi Forest becomes a real turning point or just one sharp episode in a long, grinding campaign, with much depending on whether joint operations like the Third Corps and intelligence agency assault become the template for how Ukraine fights in 2026.
Sources
Kyiv Independent, Ukrainian forces counterattack near Lyman, claim Russian regiment destroyed, December 18, 2025
United24 Media, Ukrainian Forces Break Russian Lines Near Lyman, Eliminate Entire Regiment, December 17, 2025
RBC-Ukraine, Ukraine’s forces wipe out Russian army regiment, capture troops on Lyman front, December 17, 2025