Why did Mongol armies include many non-Mongol soldiers?

Mongol armies frequently included many non-Mongol soldiers because the empire relied on a strategy of incorporating conquered peoples into their military forces. When tribes or soldiers surrendered voluntarily, they were often integrated into the Mongol ranks as federates, allowing the Mongols to maintain a massive, expanding force that was often composed of only a minority of ethnic Mongols.1

Additionally, Genghis Khan reorganized defeated foes into structured units of tens and hundreds, placing his own men in command to ensure loyalty and merit-based promotion. This bureaucratic approach allowed the army to expand indefinitely across the Eurasian Steppe. Beyond combat troops, the Mongols also actively recruited artisans and engineers from technically advanced civilizations—such as the Chinese, Persians, and Arabs—to assist with specialized tasks like the siege of walled cities. This pragmatic use of diverse human resources was a key factor in the military success of the Mongol empire.21