Ukraine's 128th Brigade Held Sumy Corridor — 7 Armored Pushes Destroyed

128th Mountain Assault Brigade held Russia's Sumy corridor for 23 days — 7 armored pushes broken, 31 vehicles destroyed. Learn the rotating outpost system, FPV drone corridors, and the intercepts that gave Ukraine advance warning each time. May 2026, Sumy Oblast — 128th Brigade, T-72/T-80 armor, PzH 2000, FPV drones, HIMARS finale. Two Russian motorized rifle regiments committed to a narrow-front assault along a secondary axis — fixed objective, fixing Ukraine away from Donetsk. The 128th Mountain Assault Brigade, repositioned three days before first contact, held without reinforcement. Their rotating outpost defense combined small forward units, pre-registered artillery, and FPV drone kill corridors that neutralized every Russian armored push. Thirty-one vehicles destroyed across seven attempts. The eighth push never launched. Intercepted radio communications showed regimental command requesting withdrawal authorization after the fifth failed assault — Moscow denied it. By day 24, both Russian regiments were combat-ineffective for six weeks. The operation stayed classified because the signals intelligence that gave Ukraine early warning of each assault timing was still active on other sectors. SteelFront breaks down how this defense worked, why Russian command couldn't adapt, and what the Sumy corridor teaches about attritional defense in the drone era.