Battle of Walaja The Battle of Walaja was a battle fought in Mesopotamia ( Iraq ) in May 633 between the Rashidun Caliphate army under Khalid ibn al - Walid and Al - Muthanna ibn Haritha against the Persian Empire and its Arab allies . In this battle the Persian army is said to have been at least three times the size of the Muslim army . Khalid decisively defeated the numerically superior Persian forces using a variation of the double envelopment tactical manoeuvre , similar to the manoeuvre Hannibal used to defeat the Roman forces at the Battle of Cannae ; however , Khalid is said to have developed his version independently . Prelude . Prophet Mohammad died on 8 June 632 , Abu Bakr succeeded him as first Caliph . Abu Bakr ' s Caliphate lasted for 27 months , during which he crushed the rebellion of the Arab tribes throughout Arabia in the successful campaign against Apostasy and restore the authority of Madinah over Arabia . Once the rebellions had been put down , Abu Bakr began a war of conquest . He launched campaigns against the Sassanid Empire and the Eastern Roman Empire ( Byzantine Empire ) and thus set in motion a historical trajectory that in just a few short decades would lead to one of the largest empires in history . After the Ridda Wars a Muslim tribal chief raided the Persian frontier towns in Iraq . After the success of these raids Abu Bakr planned to expand his empire . He started with Iraq , which was under Persian occupation at the time . After centuries of Persian power and glory , it was important for Abu Bakr ’ s expedition not to suffer a defeat , for that would confirm and strengthen the fear of the Persian military strength . To overcome these concerns he decided that the army that would battle the Persians would consist entirely of volunteers . He put in command of the army his best general Khalid ibn al - Walid . The Muslims invaded the Sassanid Persian Empire in April 633 and defeated the Sassanid army in two consecutive battles : the Battle of Chains and the Battle of River . Khalid ' s basic plan was to inflict as heavy casualties on the Persians as possible . Also , to meet as little resistance as possible along the route of his advance , his objective was to capture Hira . Concentration of Persian armies . After the Battle of River , the Rashidun Caliphate army under Khalid once again set out for Hira ; meanwhile the news of the defeat at the Battle of River reached Ctesiphon . The commanders of the defeated Persian armies were said to be some of the most experienced and most highly regarded figures at the Persian court . The Sassanian Emperor , Yazdegerd III ordered the concentration of another two armies ; Following the orders of Yazdegerd III , Persian forces began to gather at the imperial capital . They came from all towns and garrisons except those manning the western frontier with the Eastern Roman Empire . In a few days the first army was ready . The Persian court expected the Muslims to proceed along the Euphrates to North - Western Iraq , as they knew that the Muslim force would not move away from the desert , which they were expected to use to retreat to , in case of defeat . Expecting the Muslim army to move west , Yazdegerd III picked Walaja as the place at which to stop Khalid ibn al - Walid and destroy his army . The first of the new Persian armies raised at Ctesiphon was placed under the command of Andarzaghar , governor of Khurasan province . Andarzaghar was ordered to move his army to " Walaja " , where he would soon be joined by the second army . He set off from Ctesiphon , moved along the east bank of the Tigris , crossed the Tigris at Kaskar , moved south - west to the Euphrates , near Walaja , crossed the Euphrates and established his camp at Walaja . On his way to Walaja , the Persian general picked up thousands of Arabs who were willing to fight under his standard . He had also taken command of the remnants of the army that had fought in the " Battle of River and Chains " . When he arrived at Walaja he waited for Bahman , who was to join him in a few days . Bahman was the commander of the second army , and one of the top personalities of the Persian military hierarchy . He was ordered by the Emperor to take the second army to Walaja , where Andarzaghar would await him . The plan was for Bahman to be the commander of both the armies , and annihilate the outnumbered Rashidun army in one great battle . Bahman moved on a separate route to that of Andarzaghar ' s . From Ctesiphon , he marched south between the two rivers , heading directly for Walaja , but he left Ctesiphon several days after the first army started marching , causing delays . Preparation of the Muslim army . The Battle of River had been an important victory for the Muslims . While having only sustained minor casualties , the Muslims had been able to defeat a large Persian Army and to acquire a vast amount of booty . By now Khalid had organised an efficient network of intelligence agents . The agents were local Arabs who were hostile to the Persians . The agents informed Khalid about the concentration of new Persian armies in the area of Walaja and their much greater numbers . Khalid had to get to Hira , and Walaja was directly on his route . With an army of about 15 , 000 men , Khalid set off in the direction of Hira , moving at a fast pace along the southern edge of the great marsh . A few days before Bahman was expected , Khalid ’ s army arrived and camped at a short distance from Walaja . Great numbers of Sassanian Persians who had fled from earlier battles took up arms again . The survivors of the Battle of Chains joined " Qarin " and fought at the Battle of River . The survivors of the Battle of River joined " Andarzaghar " and were now encamped at " Walaja " . The Muslims faced two challenges , one strategic and one tactical : Khalid gave instructions to Suwaid bin Muqarrin to see to the administration of the conquered districts with his team of officials , and posted detachments to guard the lower Tigris against possible enemy crossings from the north and east and to give warning of any fresh enemy forces coming from those directions . Troop deployment . The battlefield consisted of an even plain stretching between two low , flat ridges , which were about 2 miles apart and 20 to 30 feet in height . The Northeastern part of the plain ran into a barren desert . A short distance beyond the North - Eastern ridge flowed a branch of the Euphrates , then also known as the River Khaseef . In May 633 , the armies deployed for battle , each with a centre and wings . The Muslim wings were again commanded by Asim bin Amr and Addi bin hatim . The Persian commander Andarzaghar deployed in the center of this plain , facing south - east , with the Western ridge behind them and their left resting on the Northeastern ridge . Khalid formed up , his army facing the Persian army . The centre of the battlefield , i . e . the midpoint between the two armies , was about 2 miles south - east of the present " Ain - ul - Muhari " , 35 miles south - east of present Najaf and 6 miles south - east to the present " Ash Sinafiyah " . The Persian cavalry was heavily outnumbered by the Muslim cavalry . It was mainly composed of heavy cavalry and was stationed behind the wings to guard the flanks . Khalid had 5 , 000 cavalry and 10 , 000 infantry with him . Knowing that his cavalry outnumbered the Persian cavalry , he designed his grand manoeuvre . His plan was the total encirclement of the Persian army using his superior cavalry . Rather than launching his cavalry via the flanks ( as Hannibal did in the Battle of Cannae . ) , Khalid made use of the terrain and positioned a part of the cavalry behind the western ridge in the battlefield . Khalid divided his cavalry into two regiments of about 2 , 000 men each , sending them behind the western ridge the night before the battle . They were instructed to attack the Persian rear at Khalid ’ s signal . The battle . Khalid faced the Persians with about 5 , 000 cavalry and 10 , 000 infantry . Cavalry was divided into two equal divisions and was deployed at the flanks . The strategy of the Persian commander in chief , Andarzaghar , was to go on the defensive and let the Muslims charge first . He planned to hold off their attacks until they were worn out , and then launch a counter - attack to rout the weary Muslim army . The first phase of the battle went according to Andarzaghar ' s plan . Khalid ordered a general attack . The Sassanid army had reserves which they employed to replace their men in the front line , giving them the upper hand over the Muslim army and helping them to carry out their scheme to wear out the Muslim army . During this time , Khalid is said to have duelled with a Persian champion of gigantic proportions known as " Hazar Mard " ( A Thousand Men ) and killed him , which was a psychological victory for the Muslims . As the first phase was over , the second phase began with the counter - attack of the Sassanid Persian army . Perhaps seeing signs of fatigue from the Muslim soldiers , Andarzaghar judged that this was the right moment for his counter - attack . At his command the Sassanians supported by the Persian heavy cavalry carried out a general attack on the Muslim front . The Muslims were able to hold them off for some time , but the Persians pressed on . On Khalid ’ s instructions the Muslim centre started retreating slowly and orderly while the wings held the ground . This created a crescent shape front allowing more and more Persian troops inside the formation . At this moment Khalid gave a signal to his cavalry and they charged the Persian right and left flank . The Muslim light cavalry could charge at incredible speed , and they could successfully attack , retreat , regroup and attack again . This mobility gave them an upper hand on the Sassanid heavy cavalry , resulting in the routing of the Persian cavalry . They attacked the flanks and rear of the Persian army and started encircling it . The main body of the Muslim army under Khalid ibn al - Walid resumed the attack against the Persian front , while at the same time extending its flanks to join hands with the cavalry to completely surround the Persians . The army of Andarzaghar was caught in a trap and could not escape . Recoiling from the assaults that came from all directions , the Sassanid army gathered in an unwieldy mass , unable to use their weapons freely . The battle was over , with heavy casualties inflicted on the Sassanid army . Nevertheless a few thousand imperial soldiers managed to escape . Andarzaghar too managed to escape . Aftermath . After annihilating another army of the Sassanid Persians and their Christian Arab allies at the final Battle of Ullais , the Muslims conquered Hira , the capital city of Mesopotamia in late May 633 . Later followed the conquest of Al - Anbar and the successful siege of Ein - al - Tamr . With the fall of the main cities the whole of Southern and Central Iraq , with the exception of Ctesiphon , came under Muslim control . In 634 , Abu Bakr ordered Khalid ibn Walid to proceed to Syria with half of his army to command the invasion of the Byzantine Empire . Al - Muthanna bin Harith Al - Shaibani was left as the successor of Khalid . The Persians , under their new emperor Yazdgerd III , raised new armies and defeated the Muslims in the Battle of the Bridge , regaining some lost ground in Iraq . The second invasion of Iraq was undertaken under Sa ` d ibn Abī Waqqās who , after defeating the Sassanid army at the Battle of al - Qādisiyyah in 636 , captured Ctesiphon . After the Battle of Nihawand in 641 a whole scale invasion of the Persian Empire was carried out by Caliph Umar .