Ukraine's Defense Forces advanced more than 15 km through underground utility tunnels into Russia's rear on the Kupiansk axis in Kharkiv Oblast, the Khartiia Corps of Ukraine's National Guard reported on 22 October. The corps called it Operation Veles. The underground advance was paired with attacks on the surface and drone strikes, hitting Russian forces from two directions, the corps told Militarnyi.

Russian troops have repeatedly crawled through gas pipelines around Kupiansk to get behind Ukrainian lines, even after Ukraine reported confident control of the city in February. This time, Ukraine went underground itself. The operation took away Russia's chance to get into Kupiansk's rear, the corps said.

The corps reported more than 30 Russian soldiers captured and Russian losses of more than 100. Militarnyi, citing the unit, put the number of Russian troops killed at over 100.

Khartiia studied how Russian troops moved through pipes before going underground itself, the corps commander, Brigadier General Ihor Obolenskyi, said.

"We watched how the enemy works underground and studied how they do it. The Russians intended to use gas pipelines to get into the rear of our troops. So we went underground ourselves. We anticipated the enemy's actions and mastered the tactics of underground combat," he said.

Boots under ground!

Asymmetric breakthrough in the Kharkiv Region: Khartiia Corps conducts the subterranean counteroffensive Operation VELES, advancing 15 km underground.

Corps Commander General Ihor Obolenskyi explains a unique operation. pic.twitter.com/qRQ93kckpK

— Khartiia Corps in English (@khartiia_eng) October 22, 2026

For the operation, troops trained physically and psychologically to fight in confined spaces, sappers and engineers prepared the underground route, and special communications, navigation, silent logistics, and life-support systems were put in place, Khartiia told Militarnyi. The operation was named after Veles, the Slavic pagan god of the underworld.

Khartiia's brigade, the R.U.H. assault regiment, the Lava drone regiment, the Achilles drone brigade, and units of Ukraine's military intelligence, including the Freedom of Russia Legion and the Russian Volunteer Corps, took part, the corps said.

Russia has used pipelines to infiltrate before

By September 2025, Russian forces had used pipelines to move troops behind Ukrainian lines three times, Ukrainian monitoring project DeepState reported on 12 September 2025. The first was in Avdiivka, the second near Sudzha, and the third near Kupiansk, where groups crossed the Oskil River through a gas pipe.

Near Sudzha in March 2025, Russian special forces walked through a pipeline that until recently had carried Russian gas to Europe, the Associated Press reported. A pro-Kremlin blogger claimed they covered about 15 km and that some spent several days inside.

Russian troops kept using the pipeline near Kupiansk this year. On 27 September, Khartiia's reconnaissance drones recorded Russian forces leading nine civilians, including children, elderly people, and a person on crutches, through the gas pipeline out of the Kupiansk community. Men of military age in civilian clothes walked alongside them, and the corps believes they were Russian soldiers using the group as cover to withdraw. Ukrainian troops held fire because of the civilians, the corps said, adding that the case has been documented for a war crimes investigation.

Why the war is moving underground

Drones, constant surveillance, and AI-assisted targeting have made the battlefield surface transparent and deadly, argue John Spencer, chair of urban warfare studies at West Point's Modern War Institute, and Col. Drew Craig, principal military engineering staff officer at NATO's Allied Rapid Reaction Corps. In an August analysis, they write that soldiers in Ukraine describe a "death zone" of some 30 km, where moving above ground can draw an attack within minutes. When firepower makes the surface too dangerous, armies have historically gone underground, as they did in World War I and Vietnam, and more recently in Gaza and Lebanon.

"Armies that cannot survive above ground must adapt below it," the authors write.

Fighting in tunnels brings its own requirements, the authors write: detecting the enemy by sound and vibration, and specialized unmanned systems that cannot rely on GPS or stable radio links. Long stretches underground also take a severe psychological and physical toll on soldiers.

Western militaries are not ready for this, Spencer and Craig write. No NATO partner maintains even general capabilities for large-scale underground warfare, and US and British efforts focused mainly on detecting and clearing tunnels rather than occupying and operating in them.

Ukrainian infantry encircled and retook the village of Kolodiazi north of Lyman without getting drawn into street fighting, while a drone battalion kept the sky above them shut, the battalion’s chief of staff told Suspilne on 18 October. The village fell during the fourth and final phase of Operation Vivaldi, Ukraine’s counteroffensive in northern Donetsk Oblast.

For years now, Russia has aimed to seize Lyman and cross the Siverskyi Donets River. It needs this area to encircle Ukraine’s fortress belt of Donetsk Oblast cities from the northwest, ISW assesses. Vivaldi’s four phases retook 277 km² and 16 settlements on that approach, and a veteran of the operation has said Ukraine’s assault troops suffered more than ten times fewer casualties than Russian forces doing it.

Drones over the infantry

The 60th Mechanized Brigade fought in all four phases of Vivaldi and took Kolodiazi in the last one, said the chief of staff of the brigade’s Fatum unmanned systems battalion, callsign Krash.

“Our task, as an unmanned systems battalion, was to escort and ‘close’ the air in front of our infantry to make it impossible for the enemy to hit it. To suppress all the firing assets possible,” he said.

The brigade’s 3rd Mechanized Battalion, the main striking force, encircled Kolodiazi and retook it without getting drawn into street fighting, Krash said. The 1st Mechanized Battalion kept Russian reinforcements out of the area, while drone crews suppressed artillery, hit supply runs, and worked against Russian drone operators.

500 troops and 200-plus vehicles

The drone battalion killed or wounded about 500 Russian troops during the fourth phase and struck Russian armored vehicles, trucks, and motorbikes, its chief of staff said.

“More than two hundred pieces of various equipment: Grad and Uragan multiple rocket launchers, various armored vehicles, tanks, armored combat vehicles. Most of all motorbikes and quad bikes, there the count runs into the hundreds. This is our enemy’s main logistics tool,” he said.

Ghost villages

The villages retaken in northern Donetsk Oblast are nearly empty of civilians, Krash said.

“It’s very typical for de-occupied settlements: these are ghost towns. You can see right away where the occupier stepped. All the settlements are under the control of the Third Army Corps, our forces stand there and prevent enemy infiltration. But civilian life in these towns is either absent or very scarce,” he said.

Third Army Corps commander Brigadier General Andrii Biletskyi reported Kolodiazi’s liberation, along with Zelena Dolyna and Lypove, when he summed up Vivaldi’s fourth phase, which secured 101 km².