Ukraine's front line has gone underground - and that's changing what defense actually means in this war. Near Kramatorsk, soldiers of the 93rd Khulodny Yar Brigade now travel between combat positions through tunnels, not only in shelters to wait out shelling. Journalists compared the growing network to a subway system: intersections, branching tunnels, multiple exits, rest stops for soldiers hauling heavy equipment. The shift happened because the old solutions stopped working. An anti-UAV net over roads used to buy some protection. It's not anymore. So Ukrainian units found routes that UAVs simply cannot observe - underground. "They are building tunnels and underground fortifications specifically so that the enemy cannot kill our soldiers with FPV UAVs," said Colonel Vitaly Serentsev, a spokesman for the 14th Corps. "It's really important for the front today, and it's one way to preserve manpower." President Volodymyr Zelensky recently visited one of these underground command posts - the photos show a fully built facility, not excavated. Some sites go further: access to trucks, parking, mixing halls, sleeping quarters, even a UAV munitions production line that the soldiers call "their underground factory." The engineering has been tested. Sergei, call sign "Marik", commands a platoon of engineer-saboteurs building fortified points with corrugated steel and three layers of wood on top. "The guys took a direct hit from 152mm cannons. The receiver held. Then a guided bomb hit ten meters away. It also held it. They all survived." Training also took place underground. The Odessa Military Academy built the country's first underground training center, designed so that classes would continue with air raid alerts. The soldiers even fly drones indoors as course work. What does that actually mean?
It is a structural answer to a battlefield where UAVs have become almost impossible to survive in the open.