I. In the first year of the first caliph, his lieutenant Caled, the Sword of God, and the scourge of the infidels, advanced to the banks of the Euphrates, and reduced the cities of Anbar and Hira. Westward of the ruins of Babylon, a tribe of sedentary Arabs had fixed themselves on the verge of the desert; and Hira was the seat of a race of kings who had embraced the Christian religion, and reigned above six hundred years under the shadow of the throne of Persia. The last of the Mondars was defeated and slain by Caled; his son was sent a captive to Medina; his nobles bowed before the successor of the prophet; the people was tempted by the example and success of their countrymen; and the caliph accepted as the first-fruits of foreign conquest an annual tribute of seventy thousand pieces of gold. The conquerors, and even their historians, were astonished by the dawn of their future greatness: "In the same year," says Elmacin, "Caled fought many signal battles: an immense multitude of the infidels was slaughtered; and spoils infinite and innumerable were acquired by the victorious Moslems." But the invincible Caled was soon transferred to the Syrian war: the invasion of the Persian frontier was conducted by less active or less prudent commanders: the Saracens were repulsed with loss in the passage of the Euphrates; and, though they chastised the insolent pursuit of the Magians, their remaining forces still hovered in the desert of Babylon. The indignation and fears of the Persians suspended for a moment their intestine divisions. By the unanimous sentence of the priests and nobles, their queen Arzema was deposed; the sixth of the transient usurpers, who had arisen and vanished in three or four years since the death of Chosroes, and the retreat of Heraclius. Her tiara was placed on the head of Yezdegerd, the grandson of Chosroes; and the same Êra, which coincides with an astronomical period, has recorded the fall of the Sassanian dynasty and the religion of Zoroaster. The youth and inexperience of the prince (he was only fifteen years of age) declined a perilous encounter: the royal standard was delivered into the hands of his general Rustam; and a remnant of thirty thousand regular troops was swelled in truth, or in opinion, to one hundred and twenty thousand subjects, or allies, of the great king. The Moslems, whose numbers were reÎnforced from twelve to thirty thousand, had pitched their camp in the plains of Cadesia: and their line, though it consisted of fewer _men_, could produce more _soldiers_, than the unwieldy host of the infidels. I shall here observe, what I must often repeat, that the charge of the Arabs was not, like that of the Greeks and Romans, the effort of a firm and compact infantry: their military force was chiefly formed of cavalry and archers; and the engagement, which was often interrupted and often renewed by single combats and flying skirmishes, might be protracted