It was while camping on the bank of the Ganges that Tamerlane received from his couriers the tidings of the disturbances on the confines of Anatolia and Georgia, of the revolt of the Christians and the ambitious designs of Bajazet. He returned to Samarcand having accomplished in a twelve month the ten years' campaign of Alexander the Great. After enjoying a few months tranquillity he proclaimed a seven years' campaign against the countries of Western Asia. To the soldiers who had served in the Indian wars he granted their choice of home or camp, but the troops of all the kingdoms and provinces of Persia were commanded to assemble at Ispahan and await the imperial standard. With an army of eight hundred thousand fighting men and a multitude of slaves so vast that it is said that they dried up the earth as they marched, he started westward. Words are lacking to describe the desolation and cruelty that attended his march and the sacking of cities. Multitudes of Christians suffered untold horrors rather than deny their faith. The cities that attempted to resist behind their walls were effaced from the earth, and upon their sites towers were erected, the walls of which were composed of living men cemented in the lime. Pursuing the people of Georgia into the gorges of the Caucasus Mountains he inflicted upon them great slaughter, and discovering many caverns into which men, women and children had fled for safety he walled up their entrances and left them to perish. Ispahan in a moment of folly having rebelled and massacred three thousand Tartars he sent back one hundred thousand soldiers with orders that every man should bring him a head on penalty of losing his own. Ispahan in consternation and horror paid this price for its revolt, and on the site of a dismantled city, a mason-wrought pyramid of a hundred thousand heads told the awful story of their doom. Proceeding westward Tamerlane laid siege to Siwas, or Sebaste, modern Siwas, a city having walls of prodigious thickness and a broad moat filled with running water. It contained one hundred and fifty thousand souls, was defended by intrepid Armenians and seemed able to defy every assault of a Tartar multitude without battering artillery to shake the walls.