At the beginning of the thirteenth century, Cinggis-qan, who had unified Mongolia, gave each of his sons and younger brothers tribes composed of several thousand-dwelling units and formed ulses. Thevarious ulses of these kinsmen, while carrying the burden of the explosive expansion of the Mongols thereafter, also formed a massive political federation under the unifying command of the Great Qa'an. The so-called Mongol Empire is nothing other than this collective body through which the kinsmen of Cinggis-qan carried out their divided rule, and its origins go back to the enfeoffment of his kinsmen at its inquguration. This problem which, in the unfolding of the history of the Mongol Empire, stands at its point of departure, has been much researched and discussed heretofore. However, not all aspects of the problem have been sufficiently clarified. Here I would like to present a preliminary essay in which I investigate a series of problems relating to the enfeoffment of Cinggis-qan's kinsmen in as total a fashion as possible. The period in which the enfeoffments were carried out is thought to have been 1207-11, the period just prior to the commencement of the subjugation of the surrounding regions. The persons who received enfeoffments were his three sons Joci, Caɣatai and Ogodei, and his three younger brothers, Joci-Qasar, Qaci'un and Otcigin. At that time, the number of tribes assigned to his three sons and three younger brothers was the same. The ulses of his three sons were positioned along the Altai on the western frontier of Mongolia, and the ulses of his three younger brothers were positioned along the Hsing-an Ling on the eastern frontier. The equality and geographical antipodosm of the eastern and western groups show that, in the period in which the Mongol state came into being, the influence of each ulus, in terms of both actual power and geography, was exactly parallel. It is thought that this was the reason why, in the age of the Mongol Empire, the various ulses of the sons in the west were called “right-wing princes" and the various ulses of the younger brothers in the east were called “left-wing princes". On both the east and west edges of the early Mongol Kingdom, which for the time being had been brought to completion through the enfeoffment of Cinggis-qan's kinsmen, were positioned the six ulses of the kinsmen. Between them stood the central ulus (Qol-un ulus) of which Cinggis-qan himself held control. With an Imperial Guard (Kesigtei) of 10, 000 men at its center it was further divided into a left guard and a right guard. Although this state structure underwent cosiderable change due to the extraordinary expansion of the Mongols thereafter, it remained the fundamental framework of the Mongol Empire, and it is likely that it was the proto-type of the several states in the Mongal line which rose and fell in Eurasia during the thirteenth and fourteenth centuries and thereafter.