One Man Army Shirogane no Ishi: Argevollen : Season 1 Episode 3

The 8th Independent Unit finally makes it back to a nearby castle before being told by their superiors they will have to move again to stop the Ingelmian advance and cover the retreat of friendly forces. Commander Samonji devises a plan to collapse the "Gates of No Retreat" by planting lots of explosives along the canyon walls, while his unit will buy time for Ardanas forces to evacuate the area.