This Juan-juan people threatened the Toba in the rear, from the north. It made raids into the Toba empire for the same reasons for which the Huns in the past had raided agrarian China; for agriculture had made considerable progress in the Toba empire. Consequently, before the Toba could attempt to expand southward, the Juan-juan peril must be removed. This was done in the end, after a long series of hard and not always successful struggles. That was why the Toba had played no part in the fighting against South China, and had been unable to take immediate advantage of that fighting. After 429 the Juan-juan peril no longer existed, and in the years that followed the whole of the small states of the west were destroyed, one after another, by the Toba--the "Hsia kingdom" in 431, bringing down with it the "Western Ch'in", and the "Northern Liang" in 439. The non-Chinese elements of the population of those countries were moved northward and served the Toba as soldiers; the Chinese also, especially the remains of the Kansu "Western Liang" state (conquered in 420), were enslaved, and some of them transferred to the north. Here again, however, the influence of the Chinese gentry made itself felt after a short time. As we know, the Chinese of "Western Liang" in Kansu had originally migrated there from eastern China. Their eastern relatives who had come under Toba rule through the conquest of eastern China and who through their family connections with Chinese officials of the Toba empire had found safety, brought their influence to bear on behalf of the Chinese of Kansu, so that several families regained office and social standing. [Illustration: Map 4: The Toba empire (_about A.D. 500_)] Their expansion into Kansu gave the Toba control of the commerce with Turkestan, and there are many mentions of tribute missions to the Toba court in the years that followed, some even from India. The Toba also spread in the east. And finally there was fighting with South China (430-431), which brought to the Toba empire a large part of the province of Honan with the old capital, Loyang. Thus about 440 the Toba must be described as the most powerful state in the Far East, ruling the whole of North China. 4 _Economic and social conditions_ The internal changes of which there had only been indications in the first period of the Toba empire now proceeded at an accelerated pace. There were many different factors at work. The whole of the civil administration had gradually passed into Chinese hands, the Toba retaining only the military administration. But the wars in the south called for the services of specialists in fortification and in infantry warfare, who were only to be found among the Chinese. The growing influence of the Chinese was further promoted by the fact that many Toba families were exterminated in the revolts of the tribal chieftains, and others were wiped out in the many battles. Thus the Toba lost ground also in the military administration.