The Inca people played very well tactically and through peaceful manner little by little were managing to unify the different people they have conquered and ruled over them. The Inca rulers were unifying the diverse people by making one language as official language of the Empire, making good infrastructure that was connecting all parts of the empire and thus allowed the people to integrate, they encouraged people to believe in their sun god Inti which made the empire religiously monogamous, and also the four regions of the empire had their own regional rulers, but all of them were under the command of one unifying Emperor which was also considered as deity.
That's my guess, this is a somewhat subjective question that really applies to your curriculum, hopefully someone who has taken the course can give a better answer.
