The Southern dynasties, except for the last Chen dynasty, were strongly dominated by the "shijia", the great families, who monopolised political power until the mid-6th century. This class was created by Cao Cao during the late Han dynasty when he attempted to consolidate his power by building an endogamous military caste of professional soldiers. This led to the rise and usurpation of the Sima family who ruled the Jin dynasty, and subsequent leaders were similarly unable to bring the other great families in line. When the Jin dynasty fled south, the weakness of the central government was greatly exacerbated, and the great families who accompanied the Emperor in his flight, along with the most wealthy clans of earlier settlers along the Zhejiang coast, were the primary power of the Eastern Jin. With the greatly increased importance of proving one's pedigree to receive privileges, there was a rise in compiling of genealogy records, and the great families moved to legally outlaw intermarriage with common families. The lower class Northern migrants were forced to become "guests" (dependents) of the great families who established private guard forces. When the Eastern Jin attempted to draft the dependents of the great families, they were quickly overthrown.