Which specialists helped Mongol armies conduct sieges?

To conduct sieges of walled cities, Mongol armies frequently relied on the expertise of artisans and engineers recruited from technically advanced conquered populations, specifically Chinese, Persian, and Arab peoples.1

These specialists provided the technical knowledge necessary to utilize advanced military technology, such as catapults and various incendiary devices, including early forms of gunpowder. By incorporating these skilled individuals into their ranks, the Mongols effectively overcame their initial limitations in siege warfare, which were otherwise better suited to open-plain cavalry maneuvers.21