Why did Mongol armies rely on Chinese, Persian, and Arab engineers during sieges?

The Mongol armies under Genghis Khan and his successors relied on foreign engineers because they were highly pragmatic and recognized that their traditional steppe warfare—centered on mobile cavalry and horse archers—was insufficient for the challenges of urban siege warfare.12

As the Mongols expanded into sedentary civilizations, they encountered fortified cities that could not be overcome by mounted archery alone. To address this, they adopted a policy of incorporating the specialized skills of conquered peoples. Chinese, Persian, and Arab engineers provided the technical expertise necessary to construct and operate advanced military engineering equipment, such as catapults and various incendiary devices.1

This reliance was part of a broader Mongol strategy of meritocracy and adaptability, where they readily employed strangers and exploited new technological possibilities to ensure their military dominance. By integrating these foreign experts, the Mongols successfully mastered complex siege techniques, which were essential for their conquests across Eurasia.21