Photographs and videos by Sasha Maslov
Ukraine’s newest battlefield lies inside a network of steel pipes deep below the ground, some barely wide enough for a person to crawl through. Before the war, these pipes carried natural gas from Russia to Ukraine. Now soldiers zip through them on electric buggies, ambushing one another with machine-gun fire and rocket-propelled grenades.
Most wars put soldiers through excruciating trials. But even by the standards of brutality set more than a century ago in the mustard-gassed trenches of World War I, the fighting in Ukraine keeps plumbing new extremes. At least 1 million troops—by some estimates, more than 2 million—have been killed or gravely wounded in this war, mostly by the drones that fill the skies above the battlefield, hunting anything that moves. Over the past few years, the omnipresent drones have produced an effective stalemate at the front, which stretches for more than 700 miles across eastern and southern Ukraine.
Aboveground, neither side has found a way to advance through what’s known as the kill zone—a new kind of no-man’s-land, dozens of miles wide, where drones can spot and attack any dugout, any vehicle, even a lonely soldier trudging through a field. “Day by day, the kill zone is expanding, getting wider and deadlier,” Brigadier General Ihor Obolensky, who commands a force of several thousand Ukrainian troops, told me. “So what’s the answer? You go underground.” There, at least, the drones cannot see you. The Russians were first to figure this out, and they have pioneered a new approach to warfare, Obolensky said. “Now we’re catching up.”
These battles, which have not been previously reported in detail, mark a broader shift in the war. Amid the intensifying barrage of Russian missiles and drones on Kyiv and other cities, many civilians have been forced to shelter underground. Schools have built subterranean classrooms. Parts of the electricity grid have moved belowground.
Weapons factories now tend to operate inside enormous bunkers. And firefights take place under the earth, one of the only areas in Ukraine that remains safe from drones and missiles.
The outcome of these battles could decide the course of the war. Throughout the year, the Russians have stockpiled supplies and mobilized soldiers in preparation for a winter offensive, several military officers and senior officials in Ukraine told me. They fear that the offensive will attempt to punch a hole through the kill zone and seize all of eastern Ukraine, which Russia could use as early as next year to launch another push toward the center of the country and its capital. Control of the gas-pipeline network in the contested region of the Donbas could give Russia a decisive advantage in the winter campaign, Obolensky told me.
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His troops, part of a military corps known as Khartiia, or “The Charter,” realized the importance of the pipeline network in the spring of 2025, when Russian troops used it to sneak behind Ukrainian lines and stage a series of surprise attacks. “They kept climbing out of the earth like devils,” Obolensky said. The infiltrations mostly took place in bad weather, when drones had a hard time spotting the Russians as they emerged from underground.
The Ukrainians responded at first by playing a deadly game of whack-a-mole. “We would try to find their exit points and cut them down when they surfaced,” Obolensky said. “But they would just keep popping up several kilometers behind our lines and attacking us.”
To better understand the threat, the general requested maps of the pipeline network from Ukraine’s state energy company. The documents showed the extent of the danger: a warren of at least 57 steel tubes running underneath the war zone, most of them one to two meters in diameter. For decades, such pipes had been used to transport gas from Siberian fields to customers in Ukraine and other parts of Europe. Ukraine cut off this trade with Russia at the start of last year. The pipeline network then went dormant, but not for very long.
Russian commanders sent their troops into the tunnels only a few weeks later, near the end of the months-long battle of Sudzha, a town in western Russia that the Ukrainians seized in August 2024. Not since the Nazi invasion of the Soviet Union in 1941 had an enemy taken Russian land by force. For the Kremlin, Sudzha stands as one of the defining humiliations of this war, and for Ukrainian President Volodymyr Zelensky, it was a significant if fleeting victory. He ordered his troops to hold that terrain, hoping to trade it against territory Russia had occupied in his country.
But his counterpart in Moscow, Vladimir Putin, had no intention of making such a deal. Instead, Putin called on support from his ally in North Korea, which sent thousands of troops to help Russia retake the wider region of Kursk. The fighting raged throughout that winter. At the start of last year, the Ukrainian hold over Sudzha began to slip, in large part because the Russians made extensive use of sewers and other tunnels to take the town back street by street.
Reports of these infiltrations horrified many Ukrainians, who found it hard to understand how Russia could motivate its soldiers to crawl for miles through a filthy pipe to reach enemy territory. This summer, a Ukrainian blogger interviewed two Russian prisoners of war who claimed to have done that. Both said they had been serving time for murder in Russian labor camps when military recruiters came to offer them their freedom in exchange for service in Ukraine, a common practice in Russia.
One of the prisoners recalled hobbling through the pipe for two days, doubled over at the waist, before reaching a hole through which he could escape into Ukraine and hide in a forest. When he radioed his commander for permission to retreat because of a leg injury, the response made clear that he had been sent to die. “There was no way back,” he said. “Only forward.”
In early 2025, soon after the Ukrainians withdrew from Sudzha, they began to see similar tactics on their own territory, including in the battle for Pokrovsk, in eastern Ukraine, Obolensky told me. His men mostly operate in the northeastern region of Kharkiv, where they have fought for more than a year to defend the city of Kupiansk, about 25 miles from the Russian border. Enemy troops kept appearing behind their lines, sometimes only one or two at a time, hiding in an abandoned building or digging a foxhole under the roots of a tree. Then they would wait for other Russians to join them before launching an ambush, Obolensky said. “The question kept arising: Where are they coming from?”
In late July, the general made his first trip into the pipes, and he came out shaken. When we met in Kyiv last month to talk about the experience, he showed me a video he had taken of himself in those moments, his face smeared with grime and his voice unsteady with emotion. “The guys working down in these pipes right now, they are heroes, unlike any other warriors I have seen,” he said into the camera of his phone.
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Other videos Obolensky shared with me show the terrifying conditions in this subterranean front. Troops from the Khartiia Corps often spend weeks underground, advancing through the pipes on repurposed coal-mining wagons powered by motors from electric scooters. The tunnels reek of residue from natural gas and other chemicals. When the Ukrainians approach an enemy position underground, firefights erupt. Both sides shoot high-caliber rifles and launch grenades, causing shrapnel and bullets to ricochet inside the metal pipes.
Explosions suck the air out of the cramped spaces, forming vacuums that leave the soldiers unable to breathe. They rely on gas masks and oxygen tanks, plugging their ears to muffle the deafening blasts. To advance, the Ukrainian troops often break through walls of sandbags erected by the Russians and push forward through incoming gunfire.
As of this week, after roughly six months of underground warfare, the Khartiia Corps had seized back control of about nine miles of pipelines in northeastern Ukraine, part of an operation they code-named Veles, after the Slavic god of the underworld. Obolensky described it as the first successful counterattack ever carried out in such conditions. But he knows that many more will be required to clear the network of pipes that Russia controls. Ukraine has, so far, retaken two. Dozens remain in Russian hands.
Sasha Maslov contributed additional reporting.