The Terdun people, having been frustrated in their assault on the second defensive line, had specifically crafted siege ladders targeting the weakness of the Shield wall—the low wall height.
Dozens of Terdun warriors arranged themselves into a shield wall formation, laboriously carrying large shields that could block arrows as they slowly advanced toward the trench.
Bows and arrows couldn't penetrate the wooden shields, and even lead shot would get stuck in the wood. Lacking the angled structures of the Bastion, the defenders of the Shield wall could only watch helplessly as the shield wall formation drew nearer to the trench.
When the advance reached within five steps of the trench, the sides of the shield wall formation opened up, and two teams of Terdun warriors, lifting the siege ladders and shouting, charged toward the Shield wall.
Other Terdun people used the large shields as cover to shoot arrows at the defenders.