A recent Russian assault in the embattled city of Kupiansk has once again thrust an uncommon, but often highly-effective tactic into the spotlight — using underground pipes to penetrate Ukrainian defensive lines. Russian units attempting to move across the Oskil River used a gas pipeline, monitoring group DeepState reported on Sept. 12, with soldiers using specially designed wheeled benches and electric scooters to maneuver. They reportedly reached the nearby village of Radkivka "without serio