Four groups of frontier peoples drew more or less advantage from the demobilization law--the people of the Toba, the Tibetans, and the Hsien-pi in the north, and the nineteen tribes of the Hsiung-nu within the frontiers of the empire. In the course of time all sorts of complicated relations developed among those ascending peoples as well as between them and the Chinese.

The Toba (T'o-pa) formed a small group in the north of the present province of Shansi, north of the city of Tat'ungfu, and they were about to develop their small state. They were primarily of Turkish origin, but had absorbed many tribes of the older Hsiung-nu and the Hsien-pi. In considering the ethnical relationships of all these northern peoples we must rid ourselves of our present-day notions of national unity. Among the Toba there were many Turkish tribes, but also Mongols, and probably a Tungus tribe, as well as perhaps others whom we cannot yet analyse. These tribes may even have spoken different languages, much as later not only Mongol but also Turkish was spoken in the Mongol empire. The political units they formed were tribal unions, not national states.

Such a union or federation can be conceived of, structurally, as a cone. At the top point of the cone there was the person of the ruler of the federation. He was a member of the leading family or clan of the leading tribe (the two top layers of the cone). If we speak of the Toba as of Turkish stock, we mean that according to our present knowledge, this leading tribe (_a_) spoke a language belonging to the Turkish language family and (_b_) exhibited a pattern of culture which belonged to the type called above in Chapter One as "North-western Culture". The next layer of the cone represented the "inner circle of tribes", i.e. such tribes as had joined with the leading tribe at an early moment. The leading family of the leading tribe often took their wives from the leading families of the "inner tribes", and these leaders served as advisors and councillors to the leader of the federation. The next lower layer consisted of the "outer tribes", i.e. tribes which had joined the federation only later, often under strong pressure; their number was always much larger than the number of the "inner tribes", but their political influence was much weaker. Every layer below that of the "outer tribes" was regarded as inferior and more or less "unfree". There was many a tribe which, as a tribe, had to serve a free tribe; and there were others who, as tribes, had to serve the whole federation. In addition, there were individuals who had quit or had been forced to quit their tribe or their home and had joined the federation leader as his personal "bondsmen"; further, there were individual slaves and, finally, there were the large masses of agriculturists who had been conquered by the federation. When such a federation was dissolved, by defeat or inner dissent, individual tribes or groups of tribes could join a new federation or could resume independent life.

Typically, such federations exhibited two tendencies. In the case of the Hsiung-nu we indicated already previously that the leader of the federation repeatedly attempted to build up a kind of bureaucratic system, using his bondsmen as a nucleus. A second tendency was to replace the original tribal leaders by members of the family of the federation leader. If this initial step, usually first taken when "outer tribes" were incorporated, was successful, a reorganization was attempted: instead of using tribal units in war, military units on the basis of "Groups of Hundred", "Groups of Thousand", etc., were created and the original tribes were dissolved into military regiments. In the course of time, and especially at the time of the dissolution of a federation, these military units had gained social coherence and appeared to be tribes again; we are probably correct in assuming that all "tribes" which we find from this time on were already "secondary" tribes of this type. A secondary tribe often took its name from its leader, but it could also revive an earlier "primary tribe" name.

The Toba represented a good example for this "cone" structure of pastoral society. Also the Hsiung-nu of this time seem to have had a similar structure. Incidentally, we will from now on call the Hsiung-nu "Huns" because Chinese sources begin to call them "Hu", a term which also had a more general meaning (all non-Chinese in the north and west of China) as well as a more special meaning (non-Chinese in Central Asia and India).

The Tibetans fell apart into two sub-groups, the Ch'iang and the Ti. Both names appeared repeatedly as political conceptions, but the Tibetans, like all other state-forming groups of peoples, sheltered in their realms countless alien elements. In the course of the third and second centuries B.C. the group of the Ti, mainly living in the territory of the present Szechwan, had mixed extensively with remains of the Yueeh-chih; the others, the Ch'iang, were northern Tibetans or so-called Tanguts; that is to say, they contained Turkish and Mongol elements. In A.D. 296 there began a great rising of the Ti, whose leader Ch'i Wan-nien took on the title emperor. The Ch'iang rose with them, but it was not until later, from 312, that they pursued an independent policy. The Ti State, however, though it had a second emperor, very soon lost importance, so that we shall be occupied solely with the Ch'iang.

As the tribal structure of Tibetan groups was always weak and as leadership developed among them only in times of war, their states always show a military rather than a tribal structure, and the continuation of these states depended strongly upon the personal qualities of their leaders. Incidentally, Tibetans fundamentally were sheep-breeders and not horse-breeders and, therefore, they always showed inclination to incorporate infantry into their armies. Thus, Tibetan states differed strongly from the aristocratically organized "Turkish" states as well as from the tribal, non-aristocratic "Mongol" states of that period.

The Hsien-pi, according to our present knowledge, were under "Mongol" leadership, i.e. we believe that the language of the leading group belonged to the family of Mongolian languages and that their culture belonged to the type described above as "Northern culture". They had, in addition, a strong admixture of Hunnic tribes. Throughout the period during which they played a part in history, they never succeeded in forming any great political unit, in strong contrast to the Huns, who excelled in state formation. The separate groups of the Hsien-pi pursued a policy of their own; very frequently Hsien-pi fought each other, and they never submitted to a common leadership. Thus their history is entirely that of small groups. As early as the Wei period there had been small-scale conflicts with the Hsien-pi tribes, and at times the tribes had had some success. The campaigns of the Hsien-pi against North China now increased, and in the course of them the various tribes formed firmer groupings, among which the Mu-jung tribes played a leading part. In 281, the year after the demobilization law, this group marched south into China, and occupied the region round Peking. After fierce fighting, in which the Mu-jung section suffered heavy losses, a treaty was signed in 289, under which the Mu-jung tribe of the Hsien-pi recognized Chinese overlordship. The Mu-jung were driven to this step mainly because they had been continually attacked from southern Manchuria by another Hsien-pi tribe, the Yue-wen, the tribe most closely related to them. The Mu-jung made use of the period of their so-called subjection to organize their community in North China.

South of the Toba were the nineteen tribes of the Hsiung-nu or Huns, as we are now calling them. Their leader in A.D. 287, Liu Yuean, was one of the principal personages of this period. His name is purely Chinese, but he was descended from the Hun _shan-yue_, from the family and line of Mao Tun. His membership of that long-famous noble line and old ruling family of Huns gave him a prestige which he increased by his great organizing ability.