Which mechanism caused the eventual breaching of Roman fortifications during prolonged sieges, despite their advanced design?

💡 Explanation

When attackers employed undermining (siege mining), soil erosion weakens the foundations because soil displacement reduces load-bearing capacity, destabilizing the structural integrity over time. Therefore, collapse via undermining results, rather than direct collapse from ballista fire, ramp overrunning or ladder scaling whose effectiveness decreases with strong foundations.

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• Which outcome resulted from the ancient Andean civilizations' usage of terrace farming on steep slopes experiencing heavy rainfall?