Lines of saltpeter were placed at the base of the walls to prevent sappers. The day before the battle Yuan personally walked along the walls inspecting their defenses and publicly declared his defiance against the Later Jin by conducting a blood pact with his remaining soldiers – a public notice of defiance was written in his blood.
The placement of saltpeter lines at the base of the walls served as a deterrent against sappers. The day before the battle, Yuan personally inspected the defenses and publicly declared his opposition to the Later Jin by making a blood pact with his remaining soldiers – a public declaration of defiance was written in his blood.