In the last resort the union of the various parts of China proceeded from the north.  The north had always, beyond question, been militarily superior, because its ruling class had consisted of warlike peoples.  Yet it was not a northerner who had united China but a Chinese though, owing to mixed marriages, he was certainly not entirely unrelated to the northern peoples.  The rule, however, of the actual northern peoples was at an end.  The start of the Sui dynasty, while the Chou still held the north, was evidence, just like the emergence in the north-east some thirty years earlier of the Northern Ch’i dynasty, that the Chinese gentry with their landowning basis had gained the upper hand over the warrior nomads.

The Chinese gentry had not come unchanged out of that struggle.  Culturally they had taken over many things from the foreigners, beginning with music and the style of their clothing, in which they had entirely adopted the northern pattern, and including other elements of daily life.  Among the gentry were now many formerly alien families who had gradually become entirely Chinese.  On the other hand, the foreigners’ feudal outlook had influenced the gentry, so that a sense of distinctions of rank had developed among them.  There were Chinese families who regarded themselves as superior to the rest, just as had been the case among the northern peoples, and who married only among themselves or with the ruling house and not with ordinary families of the gentry.  They paid great attention to their genealogies, had the state keep records of them and insisted that the dynastic histories mentioned their families and their main family members.  Lists of prominent gentry families were set up which mentioned the home of each clan, so that pretenders could easily be detected.  The rules of giving personal names were changed so that it became possible to identify a person’s genealogical position within the family.  At the same time the contempt of the military underwent modification; the gentry were even ready to take over high military posts, and also to profit by them.

The new Sui empire found itself faced with many difficulties.  During the three and a half centuries of division, north and south had developed in different ways.  They no longer spoke the same language in everyday life (we distinguish to this day between a Nanking and Peking “High Chinese”, to say nothing of dialects).  The social and economic structures were very different in the two parts of the country.  How could unity be restored in these things?

Then there was the problem of population.  The north-eastern plain had always been thickly populated; it had early come under Toba rule and had been able to develop further.  The region round the old northern capital Ch’ang-an, on the other hand, had suffered greatly from the struggles before the Toba period and had never entirely recovered.  Meanwhile, in the south the population had greatly increased in the region north of Nanking, while the regions south of the Yangtze and the upper Yangtze valley were more thinly peopled.  The real South, i.e. the modern provinces of Fukien, Kwangtung and Kwangsi, was still underdeveloped, mainly because of the malaria there.  In the matter of population the north unquestionably remained prominent.