The army next marched forward to Marakanda, now Samarkand, then merely the capital of the Sogdian satrapy, but destined to be in aftertimes the capital of the vast empire founded by Timour. It stood in the valley of the Polytimêtos (R. Kohik), a region of such exuberant fertility and beauty that it figures in Persian poetry as one of the four paradises of the world. Alexander remained for some time in this pleasant neighbourhood to remount his cavalry and otherwise recruit his forces. He then advanced to the river Jaxartes, which formed the boundary between the Persian empire and the barbarous Skythian tribes, and which the Greeks confounded with the Tanais or Don. The country was protected against the inroads of these warlike tribes by a line of fortified towns, of which the largest and strongest, Cyropolis, had been founded, as its name imports, by Cyrus. Alexander captured all these fortresses and manned them with small Macedonian garrisons; and to curb the Skythians still more effectually, founded on the banks of the Jaxartes, near where Khojent now stands, still another Alexandreia, which the Greeks for distinction’s sake called _Eschatê_, or “the Extreme.” In the midst of this undertaking, he was interrupted by the sudden outbreak of a widespread rebellion instigated by Spitamenes and his confederates. Taking immediate and energetic steps for its suppression, he in a few days recovered the seven towns; and then crossing the Jaxartes, defeated the Skythians, who with a view to aid the insurgents had mustered in great force on its right bank. After this victory he received tidings of the first serious disaster that had befallen his arms. He had sent a large force to operate against Spitamenes, who was at the time besieging the Macedonian garrison which held Marakanda. On learning that this force was approaching, the rebel chief retired down the Polytimêtos to Bokhara, and thence to the vast desert which stretches from Sogd to the Sea of Aral. Here he was joined by a large body of Skythian horsemen, and thus reinforced turned upon his pursuers, drove them back from the edge of the desert, which they had just entered, into the valley whence they had emerged, and there, amid the woody ravines of the Polytimetos, cut them to pieces almost to a man. Encouraged by this success, he returned to Marakanda and renewed the siege of its citadel, but on learning that Alexander was rapidly returning from the Jaxartes, he retraced his steps towards the desert, and reached it before the enemy overtook him. The course of the pursuit led Alexander to the scene of the late disaster. His first care was to bury the slain, and he then avenged their death by ravaging with fire and sword, in all its length and breadth, the lovely valley of the Polytimetos. He showed no mercy, but slaughtered all who fell into his hands, soldier and citizen alike. This is certainly, as Thirlwall remarks, one of the acts of his life for which it is most difficult to find an excuse.