The present province of Szechwan, in the west, had belonged to Fu Chien's empire. At the break-up of the Tibetan state that province passed to the southern Chinese empire and gave the southern Chinese access, though it was very difficult access, to the caravan route leading to Turkestan. The small states in Kansu, which dominated the route, now passed on the traffic along two routes, one northward to the Toba and the other alien states in north China, the other through north-west Szechwan to south China. In this way the Kansu states were strengthened both economically and politically, for they were able to direct the commerce either to the northern states or to south China as suited them. When the South Chinese saw the break-up of Fu Chien's empire into numberless fragments, Liu Yü, who was then all-powerful at the South Chinese court, made an attempt to conquer the whole of western China. A great army was sent from South China into the province of Shensi, where the Tibetan empire of the "Later Ch'in" was situated. The Ch'in appealed to the Toba for help, but the Toba were themselves too hotly engaged to be able to spare troops. They also considered that South China would be unable to maintain these conquests, and that they themselves would find them later an easy prey. Thus in 417 the state of "Later Ch'in" received a mortal blow from the South Chinese army. Large numbers of the upper class fled to the Toba. As had been foreseen, the South Chinese were unable to maintain their hold over the conquered territory, and it was annexed with ease by the Hun Ho-lien P'o-p'o. But why not by the Toba? Towards the end of the fourth century, vestiges of Hun, Hsien-pi, and other tribes had united in Mongolia to form the new people of the Juan-juan (also called Ju-juan or Jou-jan). Scholars disagree as to whether the Juan-juan were Turks or Mongols; European investigators believe them to have been identical with the Avars who appeared in the Near East in 558 and later in Europe, and are inclined, on the strength of a few vestiges of their language, to regard them as Mongols. Investigations concerning the various tribes, however, show that among the Juan-juan there were both Mongol and Turkish tribes, and that the question cannot be decided in favour of either group. Some of the tribes belonging to the Juan-juan had formerly lived in China. Others had lived farther north or west and came into the history of the Far East now for the first time.