Not A Unified Approach
Although his army had to be unified in their attacks, Khan preached a rather ununified approach when it came to the cultures and the religions his warriors came into contact with during his dominant period. He needed his army to welcome other ways of thought, as this would dissuade existing communities from rising up into a rebellion in a relatively easy way. This is a true display of the power of the widely referenced “divide and conquer”.
Mandatory Army Service
Khan’s army wasn’t created out of thin air. He realized that to truly dominate the regions he did, he was going to need enough men to help him get there. By making joining the army mandatory for all young people, Khan didn’t have to bank on getting people in based on their free will. This was a rule that nobody could avoid, and defecting led to the severe punishment of death or shame on your family.