Ukrainian forces discovered an unusual covert corridor: a gas pipeline through which Russian troops had been infiltrating into Kupiansk’s northern outskirts for months, bypassing fire control. When reconnaissance identified this infiltration route in December 2025, the 429th Separate Regiment of Unmanned Systems “Achilles” made a decisive choice. Three tons of explosives would seal it shut, trapping hundreds of Russian soldiers in an indefensible position.
This wasn’t just another strike on infrastructure—it was a calculated move to collapse Russian logistics supporting one of their winter campaign’s primary objectives.
How Russia’s Secret Advance Failed
Russian forces had engineered a dangerous shortcut through the industrial infrastructure left behind from the Soviet era. The pipeline ran beneath Kupiansk’s streets and outskirts, offering protection from artillery spotters and drone surveillance.
According to Commander Yurii Fedorenko of the 429th Achilles Regiment, this route allowed “the enemy to amass forces while avoiding fire control”. For weeks, small Russian assault teams crawled through or alongside this structure, assembling reinforcements for urban combat without detection.
The Day Russian Claims Shattered
Putin claimed Kupiansk was “liberated” on November 20, 2025. Three weeks later, President Zelenskyy walked into the city center, filming from just over one kilometer from encircled Russian troops. The video wasn’t theater—it was evidence.
Standing at a bullet-riddled monument bearing the city’s name, Zelenskyy positioned himself well within range of Russian drones and mortars to prove Moscow’s victory narrative was fiction. His presence signaled Ukrainian confidence that the encirclement was real and the tide had turned.
Three Tons End An Invasion Route
When commanders gave the order, the 429th Achilles Regiment moved systematically. Three tons of explosives targeted the gas pipeline—the single most critical logistics corridor keeping Russian troops supplied in northern Kupiansk. The demolition was surgical: adjacent units of the Ukrainian Defense Forces worked in coordination to cut off all potential escape routes.
Photography and video documentation showed the structure completely destroyed, collapsing under the weight of its ordnance.
Eight Months of Accumulated Fire
From April through December 2025, a single Ukrainian drone regiment had systematically dismantled Russian positions across Kupiansk. Commander Fedorenko’s unit engaged 1,877 enemy personnel, with 998 confirmed killed and 879 wounded.
Beyond the human toll, Achilles attacked 8,324 enemy shelters, destroyed 232 drone launch sites, eliminated 61 vehicles, damaged 611 more, knocked out 9 armored vehicles, and damaged 54 additional armor systems. They destroyed 8 artillery pieces and damaged 146 more.
The Counteroffensive’s Human Cost
Between September and December, Ukrainian forces conducting the broader Kupiansk counteroffensive inflicted staggering casualties on Russian forces. According to Ihor Obolienskyi, commander of the 2nd Khartiia Corps of Ukraine’s National Guard, verified Russian killed stood at 1,027, with 291 wounded and 13 captured. This figure represented only those confirmed dead—actual losses were likely significantly higher.
War correspondent Yurii Butusov reported the counterattack killed approximately 1,000 Russian soldiers, with hundreds potentially now surrounded in the city ruins.
Awaiting Surrender Or Annihilation
By December 12, Ukrainian forces had broken through to the Oskil River, severing all Russian ground lines of communication to Kupiansk. The 2nd Khartiia Corps reported encircling approximately 200 Russian soldiers in the city center. Obolienskyi stated without ambiguity: “Today we can say that the Russians in the city have been completely cut off. For a long time they could not understand what was happening. But now they know that they are surrounded”.
These soldiers faced three options: surrender, attempt a breakout through Ukrainian fire, or remain in place awaiting the final clearing operations.
Putin’s Lies, Zelenskyy’s Evidence
Russian claims of “liberation” appeared increasingly hollow when Zelenskyy appeared in person, recording from less than two kilometers away from Russian positions. Putin had publicly announced Kupiansk’s capture on November 20, 2025, awarding General Sergey Kuzovlev the Hero of Russia medal for overseeing the “liberation”.
On November 27, Putin doubled down, telling journalists that Ukrainian “enemy formations are fully liquidated there”. The propaganda gap between Moscow’s claims and battlefield reality had become undeniable.
Strategic Brilliance In Urban Warfare
Commander Ihor Obolienskyi’s 2nd Khartiia Corps of the National Guard executed a textbook counteroffensive operation under conditions of extreme urban complexity. In September 2025, as Russian forces pushed deeper into Kupiansk, the Ukrainian military created a dedicated “search-and-strike group” to counter the assault.
Khartiia coordinated with the 475th “Code 9.2” Assault Regiment, the 92nd Assault Brigade, military intelligence forces, and the 144th Mechanized Brigade. This multi-unit approach allowed Ukrainian forces to systematically clear neighborhoods, establish fire control over escape routes, and finally encircle Russian forces.
How Cutting The Pipeline Changed The War
The gas pipeline wasn’t merely a footnote in Kupiansk’s urban warfare—it represented the difference between Russia’s capacity to sustain an urban assault and its collapse. With ground supply lines severed and the pipeline destroyed, Russian soldiers remaining in the city depended entirely on aerial resupply via drone drops. This created a critical vulnerability: Ukrainian air defense and drone counter-operations could disrupt deliveries, forcing a choice between starvation or surrender.
The destruction of the pipeline turned Kupiansk from a contested urban zone into a potential Russian death trap.
The Hidden Cost
Among the rubble of northern Kupiansk, approximately 500 local residents remained trapped in the contested areas. Russian forces were using these civilians as human shields, complicating Ukrainian clearing operations. The 2nd Khartiia Corps acknowledged the moral and tactical weight of this situation, noting that the operation would require extensive house-to-house clearance while protecting noncombatants.
Zelenskyy’s visit underscored this responsibility: Ukraine’s forces were not pursuing a scorched-earth campaign, but rather a deliberate and careful recapture of their own territory.
The Drone Commander Leading Modern Warfare
The 429th Achilles Regiment represents a new generation of Ukrainian military innovation, and Yurii Fedorenko embodies that transformation. Since 2014, Fedorenko had fought in various conflicts in Ukraine, eventually forming a drone reconnaissance company that evolved into the Achilles Strike Aviation unit.
His regiment was among Ukraine’s first dedicated strike drone formations, pioneering tactics now studied by Western militaries. Under his command, Achilles delivered precision strikes, coordinated air support, and integrated drone reconnaissance with traditional artillery, rewriting doctrinal playbooks in real-time.
Putin’s Winter Gamble Unraveling
Russia’s 2025 winter offensive had been designed to capture Ukraine’s remaining northeastern holdings before diplomatic pressure forced negotiations. Kupiansk was positioned as the linchpin—if Russia held the city, Moscow could claim territorial victories to leverage in peace talks.
Instead, Ukraine’s December counteroffensive shattered this calculation. The loss of 1,000+ troops, the destruction of logistics infrastructure, and the encirclement of 200 soldiers turned the operational narrative on its head.
Victory On The Horizon
As of mid-December 2025, Ukrainian forces continued clearing operations in northern Kupiansk under extremely challenging conditions. Russian soldiers in the center of the city faced imminent isolation from all supply sources. Obolienskyi indicated that the final liberation of Kupiansk remained ongoing, with house-to-house combat continuing, but Ukrainian forces were “getting the job done.”
The destruction of the infiltration pipeline meant Russian reinforcement was virtually impossible. Casualties and surrender seemed the only paths forward for the encircled contingent. This December counteroffensive may ultimately prove to be the turning point in the 2025 military balance of the Kharkiv region.