544 ACROSS THE PEI-SHAN TO BARKUL [Chap. XV
year to succour I-wu marched to the P`u-lei lake. But the evasive chief had retreated, and the Chinese retired without having achieved any success.25 This is one of the last events relating to the ` Western kingdoms ' that the Later Han Annals record, and with the steady decay of Chinese influence beyond the frontiers that accompanied the internal disintegration of the Empire during the closing reigns of the Later Han dynasty, our sources of information about the territories along the Trien-shan dry up for centuries.
It is probable enough that the valleys on the northérn slopes of the Tien-shan offering attractive grazing grounds continued during the succeeding centuries to be haunted by tribes of the Hsiung-nû or Huns, and subsequently, after these had moved westwards, by the Juan-juan or by Turkish tribes like the Tölös subject to the latter. But it is not until the beginning of the seventh century that, owing to the relations which China had resumed with Central Asia under the Sui emperors, and which the forward policy ' of the founder of the Trang dynasty and his successors was soon to develop, some light is again thrown upon the conditions prevailing in this region by the Chinese
records accessible to me. The. Tölös or Tieh-lo j of the Chinese, later famous under the
name of Uighur, after their victory over the Kagan of the Western Turks in A. D. 605, are said to have become masters of I-wu or Hâmi as well as of Kao-ch`ang (Turfân) and Yen-ch`i (Kara-shahr).2° The chief of I-wu, who about A. D. 6o8 made his submission to the Sui Emperor, is designated by a Turkish title, and it is probable that he belonged to a tribe established in the Tien-shan valleys to the north 27 I-wu subsequently passed again under the domination of the Western Turks, and Chinese control was not definitely established there until A. D. 630. It is significant, in view of the political interdependence which, as explained above, geographical conditions create between the Hâmi oasis and the valleys adjoining it north of the Teien-shan, that this natural base for the rang conquest of the ` Western Kingdoms ' was not finally secured until the Chinese had in A. D. 63o won their decisive victory over the souverain chief of the Northern Turks.28
An attack which Chet' Wên-trai, king of Kao-ch`ang or Turfân, and the Kagan of the Western Turks directed some years later against Hâmi was followed by a great Chinese expedition in A. D. 640, which led to the conquest of Turfân and, in its ultimate effects, to the firm establishment of
Chinese supremacy over the territories occupied by the Western Turks. To this expedition we owe an interesting epigraph set up in the same year on the top of the Barkul pass and still to be found
there. This long inscription, which is engraved on a stélé and has been edited and translated by M. Chavannes from an impression secured by M. Bonin, commemorates the exploit of the general
Chiang Hsing-pên r7 4 commanding one of the three armies sent by the Emperor T`ai-tsung
for the subjection of Turfân. In the fifth month of the Chinese year corresponding to A. D. 64o, he took his troops to the top of Mount Shih-lo-Haan FI; thence ascending to Hei-kan-so ` they cut down the trees until the forests of the mountains were exhausted ' and within a month constructed siege machines such as ballistae and other engines of war with which to meet the task awaiting the ` army of Kao-ch`ang '. Neither the redundant rhetorics of the praise bestowed upon the commander and his valiant troops, nor the poetical eulogy with which the inscription closes, furnish local data.29 But there can be no doubt that the force moved to the pass and thence to the
heights of Hei-kan-so )fi because, then as now, no forest furnishing an adequate supply of
25 See Chavannes, T`oung-pao, 1907, p. 214. 20 See Chavannes, Turcs occid., p. 89, note 3.
27 See ibid., p. 169, note 8. 28 Cf. ibid., p. 170.
29 The greatness of the physical difficulties which the march of the large Chinese forces across the Pei-shan desert must have involved is, however, reflected in the third strophe