Hierarchy of Social Classes. Although the Mongols had established Yuan dynasty rule over all of China, their conquest was not completed without difficulty. Chinese in both northern and southern China organized resistance movements against Mongol control and employed guerilla warfare, or individuals refused to collaborate with their conquerors. Facing hostility from the Chinese, Mongol leaders employed a policy of ethnic discrimination by setting up a strictly enforced hierarchy of social classes, ordered in descending level of importance: from the Mongols, semu ren (Western and Central Asians), han ren (northern Chinese), to the nan ren (southern Chinese). During the Yuan period many foreigners, especially Muslims from Central and West Asia, were employed by the Mongol court as advisers, civil officials, military officers, financial managers, tutors, translators, physicians, astronomers, and skilled craftsmen. These non-Chinese foreigners, or semu...