While the Samanides were thus harassed by the powerful Daylamites in the west, by the growing power of Sabuktagin in the south, and the fear of insubordination in their own states, a force still more formidable had arisen on their northern frontier, where a Turkish state had been founded which extended from Kashghar to the Sea of Aral. The relations of this state with its southern neighbours were at first of a peaceful and even friendly character; but when the nomads perceived that Iranian authority was on the wane they began to cast longing eyes across the Jaxartes. They probably belonged to the tribe of UÏghur, which had been the first to separate from the main body of the Turkish race and settle down in a home on the slopes of the Tien-shan.244 According to the Mohammedan historian Juvayni,245 the UÏghurs originally came from the valley of the Orkon River. The first king whose name has come down to us was Buku Khan, whom tradition has identified with the great Afrasiyab.246

Buku Khan, having learnt in a dream that he would possess the entire world, assembled his troops and sent his brothers to wage war against the Mongols, Kirghiz, Tanguts, and Khitays.247 They returned to their dwelling-place with great booty, and founded the city of Urdu Balik. Buku Khan again dreamt that a piece of jade was given him with the assurance that as long as he preserved it he would rule the world. The prospect induced him to turn his arms to the west and enter Turkestan, where he built the city of Balasaghun.248 We know from Chinese sources that these UÏghurs249 had their abode in the seventh century in the north-west of Mongolia; that in the eighth century they dwelt near the place where, in the five hundred years later, the Mongols built Karakorum. In the ninth century their empire in Mongolia was destroyed by the Kirghiz, when they were dispersed, and apparently split into two parties. The eastern branch came into contact with Chingiz Khan. After and thenceforward they appear in the Mongol-Chinese annals as under the name of Wei-wu-rh.250 Of the Western UÏghurs little is known, but they may be identified with the Eastern Turks of Mohammedan authors of the eleventh and twelfth centuries.251 The first of the UÏghur Khans of Turkestan who plays any great part in Mohammedan history is Boghra Khan, whose capital was Balasaghun, and who ruled over Kashghar (called Urdu Kend), Khotan, Karakorum, Taras, and Farab (Otrar).252 He was contemporaneous with Nuh III., seventh of the Samanide line, whose reign was characterised by the utmost confusion and anarchy. Two of Nuh’s most powerful nobles—Abu `Ali Simjur, governor of Khorasan, and Fa´ik, governor of Herat, whose insubordination had received severe but well-merited punishment at the hands of their master—made treacherous overtures to Boghra Khan, and invited him to attack Nuh. The invitation was accepted with alacrity by the UÏghur prince, who at once set out for Samarkand, which was delivered over to him by the faithless Fa´ik, whom Nuh had intrusted with its defence. The feeble representative of the Samanides, thus betrayed, fled from his capital, which Boghra Khan shortly after entered in triumph, and became practically master of Transoxiana. But the climate of Bokhara did not suit him. He set out for his home, when death overtook him ere he had gone many stages, A.H. 383 (993). Meanwhile Nuh re-entered Bokhara and regained possession of his dominion. But though he was heartily welcomed by the people he did not feel secure from the treachery of his nobles, and on this account he invited the great Sabuktagin, in the year A.H. 384 (994), to come to his aid. Sabuktagin immediately hastened over the mountain passes at the head of 20,000 men, and, crossing the Oxus, joined Nuh at Kesh. Seconded by his son Mahmud, he gained three victories over the rebel lieutenants at Herat, Nishapur, and finally at Tus. Fa´ik had in the meanwhile fled to Ilik Khan, the son and successor of Boghra Khan, and Bokhara was threatened with a second UÏghur invasion. In reply to the menace, Sabuktagin, who had quarrelled with Nuh, concluded a peace with Ilik, and appointed the rebellious Fa´ik governor of Samarkand.

In A.H. 387 (997) both Sabuktagin and Nuh died, and were respectively succeeded by the valorous and talented Mahmud, and by Mansur II. who exhibited qualities precisely the reverse.

Transoxiana fell into the power of Ilik Khan, while Mahmud of Ghazna gained possession of Khorasan. Turks had long held high office in the states of Islam in Central Asia, as well as in Baghdad and in Egypt, where they had founded a powerful dynasty. It was, therefore, no great change for them to find themselves, as a nation, masters of the extensive kingdom of which Bokhara was the capital.

Mansur II., after a reign of less than two years, was deprived of sight by one of his discontented courtiers named Bektuzun; and `Abd el-Melik II., a mere child, was set up in his stead. All power was now concentrated in the hands of Fa´ik and Bektuzun. When news of these events reached Ilik Khan in Kashghar he sent a message to `Abd el-Melik to the effect that he would speedily take measures to protect him. Bektuzun immediately set out to oppose Ilik Khan, but he was unsuccessful, and in A.H. 389 (999) Ilik Khan entered Bokhara. Instead, however, of helping the young prince, he cast him into prison, where he soon afterwards died.253 When, in A.H. 389 (999), Ilik Khan254 wrested Transoxiana from the Samanides, their capital was removed to Bokhara. In A.H. 398 (1007) they attempted to establish themselves south of the Oxus, but were driven back by Mahmud of Ghazna, and henceforward their territory was restricted to Transoxiana, Kashghar, and Eastern Tartary.255

About the beginning of the tenth century a prince of the hereditary house of the Khans of Kashghar, named Satuk Boghra Khan,256 became the first convert in that country to Islam, which he proceeded to force upon his subjects at the point of the sword, in the face of a determined and protracted opposition which prevented its spread beyond the limits of his own territory. It was only on the downfall of the Samanides that the creed of Mohammed, through proselytising zeal—of Mahmud in the direction of Hindustan, and of Ilik Khan in that of Turkestan—received a fresh impetus, and spread north, south, and east with a rapidity only equalled by the violence employed by its propagators.257

According to Narshakhi,258 Ilik Khan died in A.H. 403 (1012), and was succeeded by his brother Toghan Khan, who, a few days after his accession, was attacked by what appeared to be an incurable malady. The Sultans of Khitay and Khotan, thinking to take advantage of his helpless state, advanced with an enormous host to attack his dominions.259 But, on hearing of the approaching invasion, the Khan miraculously recovered his health and forthwith set out to oppose his enemies. We are told that they retreated without striking a blow as soon as they learnt that their quarry had regained his strength, but were hotly pursued and harassed by the Khan for three months.

Toghan Khan died in A.H. 408 (1018). He is spoken of in terms of the highest praise, both on account of his piety and his learning. His successor was Arslan Khan, who, however, was unable to preserve the integrity of his kingdom. Coming into conflict with Sultan Mahmud, he was defeated and killed in the year A.H. 410 (1020).

Kadir260 Khan, who now ascended the throne at Samarkand, is said to have brought the whole of Kashghar and Khotan under his subjection. He died in A.H. 423 (1031), and was succeeded by his son Arslan Khan. During his reign he received a deputation from some Turks of Tibet, who, hearing of his justice and clemency, asked permission to settle in the neighbourhood of Balasaghun. He granted their request, and when they arrived he tried to compel their acceptance of Islam. This they refused, but as they were otherwise loyal and obedient he gave way and allowed them to remain in a state of heathenism.261 Arslan Khan was overthrown in A.H. 425 (1033) by his brother Boghra Khan, during whose reign the immigrant Turks embraced Islam (A.H. 432).262 He died by poison in A.H. 439 (1047), and was succeeded by his son Ibrahim—the last chief of the house of Boghra Khan.263

The kingdom of Kashghar seems shortly afterwards to have fallen into the hands of another branch of the Eastern UÏghurs, called by Narshakhi the Tufghaj,264 the first of whose representatives, Ibrahim, was killed in battle against Alp Arslan, the Seljuk, in A.H. 472 (1079), and was succeeded by his brother Khidhr Khan.265 He apparently died in the same year, when his son Ahmed Khan came to the throne. The latter, in A.H. 482 (1089), was attacked and defeated by Melik Shah, and sent prisoner to Isfahan; but soon afterwards he was reinstated as governor of Transoxiana. In 488 he was condemned to death by the mullas or doctors of Samarkand, on the ground that he professed heretical tenets acquired during his residence in Persian `Irak. After him Mas`ud Khan266 reigned for a short period, and was succeeded by Kadir Khan, who in A.H. 495 (1101) perished in an insurrection fomented by him against Sanjar, the then governor of Khorasan.

The next ruler of Samarkand was Mohammad Khan267 ibn Sulayman, who in A.H. 503 (1109) successfully defended his capital against the attack of a large Turkish force under a certain Saghir Beg. He held this post until his death, and apparently continued in his loyalty to Sanjar, who, as we have seen, ascended the throne of the Seljuks in 511. We are not told when he died, but Narshakhi says that his son Nasr Khan was killed during a revolt in Samarkand in A.H. 523 (1128). On the death of his father, Nasr’s son Mohammad Khan wrote to inform Sanjar of what had passed. Sanjar thereupon set out with a force to establish order in Samarkand, but when he approached the town Mohammad Khan sent him an insolent message that the Sultan would do well to retreat, inasmuch as he (Mohammad) had subdued his opponents. Sanjar was much incensed, and promptly invested the city. After a protracted siege he captured Samarkand and took Mohammad prisoner, A.H. 524 (1129). A new governor was now appointed, but he died two years later, when the reins of power were given to Mahmud Khan, the son of Mohammad.268

In the meanwhile another mighty host was advancing on Transoxiana; but before describing their progress we must retrace our steps and recount the downfall of the Ghaznavides and the rise of the great Seljuk dynasty of Persia.