The Arabs, upon this repulse, retired to El Lis; and Al Mothanna sent to Omar for reinforcements, which speedily arrived under the command of Jarir, son of Abdallah.  Al Mothanna was preparing to resume the offensive when the Persians anticipated him.  A body of picked troops, led by Mihran a general of reputation, crossed the Euphrates, and made a dash at Hira.  Hastily collecting his men, who were widely dispersed, Al Mothanna gave the assailants battle on the canal El Boweib, in the near vicinity of the threatened town, and though the Persians fought with desperation from noon to sunset, succeeded in defeating them and in killing their commander.  The beaten army recrossed the Euphrates, and returned to Otesiphon without suffering further losses, since the Arabs were content to have baffled their attack, and did not pursue them many miles from the field of battle.  All Mesopotamia, however, was by this defeat laid open to the invaders, whose ravages soon extended to the Tigris and the near vicinity of the capital.

The year A.D. 636 now arrived, and the Persians resolved upon an extraordinary effort.  An army of 120,000 men was enrolled, and Rustam, reckoned the best general of the day, was placed at its head.  The Euphrates was once more crossed, the Sawad entered, its inhabitants invited to revolt, and the Arab force, which had been concentrated at Cadesia (Kadisiyeh), where it rested upon a fortified town, was sought out and challenged to the combat.  The Caliph Omar had by great efforts contrived to raise his troops in the Sawad to the number of 30,000, and had entrusted the command of them to Sa’ad, the son of Wakas, since Al Mothanna had died of his wound.  Sa’ad stood wholly on the defensive.  His camp was pitched outside the walls of Cadesia, in a position protected on either side by a canal, or branch stream, derived from the Euphrates, and flowing to the south-east out of the Sea of Nedjef.  He himself, prevented by boils from sitting on his horse, looked down on his troops, and sent them directions from the Oadesian citadel.  Rustam, in order to come to blows, was obliged to fill up the more eastern of the branch streams (El Atik), with reeds and earth, and in this way to cross the channel.  The Arabs made no attempt to hinder the operation; and the Persian general, having brought his vast army directly opposite to the enemy, proceeded to array his troops as he thought most expedient.  Dividing his army into a centre and two wings, he took himself the position of honor in, the mid-line with nineteen elephants and three fifths of his forces, while he gave the command of the right wing to Jalenus, and of the left to Bendsuwan; each of whom we may suppose to have had 24,000 troops and seven elephants.  The Arabs, on their side, made no such division.  Kaled, son of Orfuta, was the sole leader in the fight, though Sa’ad from his watch-tower observed the battle and gave his orders.  The engagement began at mid-day and continued till sunset.  At the