Battle of Jalula Battle of Jalula was fought between Sassanid Empire and Rashidun Caliphate soon after conquest of Ctesiphon . After the capture of Ctesiphon , several detachments were immediately sent to the west to capture Qarqeesia and Heet the forts at the border of the Byzantine empire . Several strong Persian armies were still active north - east of Ctesiphon at Jalula and north of the Tigris at Tikrit and Mosul . The greatest threat of all was the Persian concentration at Jalula . After withdrawal from Ctesiphon , the Persian armies gathered at Jalula north - east of Ctesiphon , a place of strategic importance from where routes led to Iraq , Khurasan and Azerbaijan . The Persian forces at Jalula were commanded by General Mihran . His deputy was General Khurrazad a brother of General Rostam Farrokhzād , who had commanded the Persian forces at the Battle of Qadisiyyah . As instructed by the Caliph Umar , Saad ibn Abi Waqqas reported all the matter to Umar . The Caliph decided to deal with Jalula first ; his plan was first to clear the way north before any decisive action against Tikrit and Mosul . Umar appointed Hashim ibn Uthba to the expedition to Jalula . Some time in April 637 , Hashim marched at the head of 12 , 000 troops from Ctesiphon and after defeating the Persians at the Battle of Jalula , laid siege to Jalula for seven months , until it surrendered on the usual terms of Jizya . Prelude . After the capturing Ctesiphon , several detachments were immediately sent west to capture Qarqeesia and Heet , forts at the border of Byzantine empire . Strong Persian garrisons north - east of Ctesiphon at Jalula and north of Tigris at Tikrit and Mosul , were threat to Muslim invaders . The greatest threat of all was the Persian concentration at strategic fort of Jalula . The Persian forces at Jalaula were commanded by General Mihran . His deputy was General Khurrazad a brother of General Rostam Farrokhzād , who commanded Persian forced at Battle of Qadisiyyah . Jalula was a town of great strategic importance , a bottle - neck to Northern Iraq . To have Jalula under the rule meant to have the gate to Northern Iraq . Persians therefore expected an attack on Jalula . Defense of Jalula was also very important for the strength of Empire and maintain order in the far flung frontiers of the Persian Empire . As instructed by the Caliph Umar , Saad ibn Abi Waqqas , Muslim commander in chief on Persian front , reported all the strategic situation to Umar . Who decided to deal with Jalula first , his plan was first to clear his rear before any decisive action further north against Tikrit and Mosul . Umar appointed Hashim ibn Uthba to the expedition of Jalula . Some time in April 637 , Hashim marched at the head of 12 , 000 troops from Ctesiphon and made contact with Persians out side Jalula fort . Battlefield . At Jalula , both the flanks of Persians and Muslims rested upon natural obstacles . " Diyala River " on east and broken ground on the west . Broken ground was unsuitable for cavalry and even the movement of infantry " en masse " was difficult and would have exposed them to Persian Fire - Power . Opposing plans . Mihran , the Persian commander at Jalula , was a veteran general who had fought Muslims in Qadisiya and knew well of the Muslim ' s tactics . He dug entrenchments and placed Caltrop s in front of them , to slow down Muslim advance . The Persian troops intended to weir Muslims down by letting them launch a frontal attack thus exposing themselves to Persian Archers and siege engines led Artillery . The caltrops also hindered the speed of Muslim cavalry and infantry . Mihran deployed his army in classical defensive formation with the intention of launching the attack when Muslims have suffered enough and the nucleus of their power has been destroyed . Hashim , the Muslim commander , on reaching the battlefield , analyzed that the Persians cannot be attacked from the flanks due to those natural barriers and approaching them from the front would be costly . He decided to lure the Persians out of defenses of entrenchments and caltrops . Hashim planned to launched a frontal attack and made a feint retreat under Persian fire and once the Persians are away from trench his cavalry will capture the bridge on the trench , cutting off Persian ' s escape route . Battle . The battle begun with Muslim ' s frontal attack , after engaging for some time Muslims feint a retreat and fall back in an organized manner . Mihran , sensing the time is on hand to launch an offensive for him , ordered the entrenchments to be bridged . Once the Persian army had attained the battle formation he ordered a general attack . Up till now the battle had progressed as both the commanders had planned . Once Mihran engaged his troops in an open battlefield , Hashim decided to carry out his maneuver . He dispatched a strong cavalry regiment under one of his most illustrious cavalry commanders ; Qaqa ibn Amr , to capture the bridge over the entrenchments . The bridge was not heavily guarded as virtually all the Persian troops available were used to assault Muslim main body . Qaqa maneuvered around Persian right flank quickly captured the bridge at their rear . The news of a strong Muslim cavalry detachment in their rear was a serious setback to Persian morale . Hashim launched a frontal attack with Muslim infantry while Qaqa stuck at Persian rear with his cavalry . Persian troops were trapped between Muslim army and the natural barriers on the battlefield . Nevertheless thousands of them managed to escape and reached the Jalula fortress . Aftermath . Persian suffered heavy casualties and the battle ended in complete Muslim victory . After the battle Hashim laid siege to Jalula . Persian emperor Yazdegerd III was in no position to set a relief force to Jalula and the fortress surrendered to Muslims seven months later on the terms of annual payment of Jizya ( " tribute " ) . After capturing Jalula Muslims captured Tikrit and Mosul , completing their conquest of Iraq . After conquest of Iraq ( region west of Zagros mountains ) Umar decided to consolidate the conquered territory . He apparently for the time being , did not wanted further conquest . He was almost on defensive until the consistent Persian raids in Iraq made him to launch a whole scale invasion of the Persian empire .