Which vulnerability was exploited when siege engines damaged stone walls in medieval castles?

💡 Explanation

When siege engines like trebuchets or catapults impact stone walls, tensile stress concentration occurs at the mortar joints between stones because the mortar is weaker in tension than the stone itself, leading to cracking. Therefore tensile stress is the vulnerability, rather than compressive instability, shear separation, or torsional stress that don't manifest primarily in this situation.

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