The motives which induced Nadir to proceed upon this expedition were soon apparent. He had no desire to extend the boundary of his empire in a direction where he knew it could not be maintained, but he wished to visit upon the inhabitants of this part of Tartary those calamities which they were in the annual habit of inflicting upon the frontier provinces of Persia. Abul Fyze Khan, who was the ruler of the Usbegs at this period, boasted a lineal descent from Genghis; but he appears to have inherited none of the spirit of his great ancestor. He was terrified into submission at the approach of Nadir, and sent his vizier to deprecate the wrath of that monarch. The minister was well received, but told that his master must immediately surrender if he desired to save himself from destruction and his country from ruin. While these negotiations were carried on the Persian army advanced by rapid marches to Bokhara, and on August 23d, five days after they had crossed the Oxus, encamped within twelve miles of that capital, where his short expedition was brought to a close by the personal submission of Abul Fyze Khan, who, attended by all his court, proceeded to the tents of Nadir Shah, and laid his crown and other ensigns of royalty at the feet of the conqueror, who assigned him an honorable place in his assembly; and a few days afterward restored him to his throne on the condition that the Oxus should remain, as it had been in former periods, the boundary of the two empires. This treaty was cemented by an alliance between the daughter of the ruler of Bokhara and the nephew of his conqueror; and after its conclusion a great number of Tartars were, with the concurrence of their own monarch, enrolled in the Persian army, whose commander probably esteemed the services of these hardy warriors as of more consequence to the peace of his own dominions and the fulfilment of his future views of ambition than all the wealth he had brought from India.