- May 2009
According to the Yuanshi two Muslim engineers named Isma'il and Ala Al-din were sent by the Ilkhan Abaqa to assist Khubilai Khan with the siege of Xinagyang in late 1272. They built a mangonel and a catapult capable of hurling huge projectiles that destroyed everything they hit. By early 1273 the defenders surrendered. There's no mention of the walls being breached, but at that point it doesn't really matter. Once the enemy has the power to rain down hell on your city from the outside, eventually you're going to surrender, even if the walls are perfectly intact.