At the start of the year, Russian troops began infiltrating deep behind Ukrainian lines several miles and a river away from their own positions.
They hadn’t crossed through minefields or through treelines stalked by drones. They had gone under them.
It wasn’t the first time Russian soldiers had used hundreds of miles of Soviet-era gas pipelines to crawl behind Ukrainian positions to cut their way through to the surface and stage surprise attacks. But near the city of Kupyansk, Ukraine is now fighting back underground, leading to pitched battles in the dark to stem the Russians’ subterranean advance.
