Battle of Gaugamela The Battle of Gaugamela ( ; ) took place in 331 BC between Alexander the Great and Darius III of Persia . Also called the Battle of Arbela , it was a decisive victory for the Macedonians and led to the fall of the Persian Empire . Location . Darius chose a flat , open plain where he could deploy his larger forces , not wanting to be caught in a narrow battlefield as he had been at Issus two years earlier , where he was unable to deploy his huge army properly . Darius had his soldiers flatten the terrain prior to the battle , so as to give his 200 war - chariots optimal conditions . However , this did not matter . On the ground were few hills and no bodies of water that Alexander could use for protection , and in the autumn the weather was dry and mild . The most commonly accepted opinion about the location is ( ) , east of Mosul in modern - day northern Iraq – suggested by Sir Aurel Stein in 1938 ( see his " Limes Report " , pp . 127 – 1 ) Background . During the two years after the Battle of Issus , Alexander occupied the Mediterranean coast and Egypt . He advanced from Syria against the heart of the Persian empire , crossing the Euphrates and Tigris rivers without any opposition . Darius was building up a massive army , drawing men from all parts of his empire , more than 250 , 000 soldiers ( including more than 42 , 000 cavalry ) against approximately 47 , 000 Macedonian soldiers ( including around 8 , 000 cavalry ) . Just before the battle , Darius offered Alexander a generous peace agreement : he would cede half the Persian Empire if Alexander ceased his invasion of Persia , but Alexander declined without any consideration . One of Alexander ' s generals , Parmenion , said that if he were Alexander he would gladly accept the more - than - generous offer . Alexander replied , " And I would too , if I were Parmenion . " Time of attack . On the eve of battle Alexander ' s generals , including Parmenion , suggested that to counter the overwhelming number of Persians , a surprise night attack should be launched . Alexander dismissed this , proclaiming that he would not " steal his victory " . This was either a lucky move or a stroke of genius : Darius , fearing a night attack , kept his army awake and on alert for the whole night , while Alexander ' s was allowed to sleep . The next morning , Alexander over - slept . When his concerned generals woke him , he stated matter - of - factly that the battle had already been won . Size of Persian army . Modern estimates . Some ancient Greek historians suggest that the main Persian army numbered between 200 , 000 and 300 , 000 , but some modern scholars suggest that it was no larger than 50 , 000 because of the logistical difficulty of fielding more than 50 , 000 soldiers in battle at the time . However , it is possible that the Persia n army could have numbered over 100 , 000 men . One estimate is that there were 25 , 000 peltast s , 10 , 000 Immortals , 2 , 000 Greek hoplite s , 1 , 000 Bactria ns , and 40 , 000 cavalry , 200 scythed chariot s , and 15 war elephant s . Hans Delbrück estimates Persian cavalry at 12 , 000 because of management issues , Persian infantry ( peltast ) less than that of the Greek heavy infantry , and Greek mercenaries at 8 , 000 . Warry estimates a total size of 91 , 000 ; Welman 90 , 000 ; Delbrück ( 1978 ) 52 , 000 ; Engels ( 1920 ) and Green ( 1990 ) no larger than 100 , 000 . Ancient sources . According to Arrian , Darius ' s force numbered 40 , 000 cavalry and 1 , 000 , 000 infantry , Diodorus Siculus put it at 200 , 000 cavalry and 800 , 000 infantry , Plutarch put it at 1 , 000 , 000 troops ( without a breakdown in composition ) , while according to Curtius Rufus it consisted of 45 , 000 cavalry and 200 , 000 infantry . Furthermore according to Arrian , Diodorus , and Curtius , Darius had 200 chariot s while Arrian mentions 15 war elephants . Included in Darius ' s infantry were about 2 , 000 Greek mercenary hoplite s . What we see here is that ancient historians agree on the size of the Persian infantry : ' one million infantry stretched over four kilometers wide ' . Modern writers try to downgrade both the size of the Persian army and the glorious victory of the Greeks . While Darius had a significant advantage in numbers , most of his troops were of a lower quality than Alexander ' s . Alexander ' s pezhetairoi were armed with a six - metre spear , the sarissa . The main Persian infantry was poorly trained and equipped in comparison to Alexander ' s pezhetairoi and hoplites . The only respectable infantry Darius had were his 10 , 000 Greek hoplites and his personal bodyguard , the 10 , 000 Persian Immortals . The Greek mercenaries fought in a phalanx , armed with a heavy shield but with spears no longer than three metres , while the spears of the Immortals were 2 metres long . Among the other Persian troops , the most heavily armed were the Armenia ns who were armed the Greek way , and probably fought as a phalanx . The rest of Darius ' s contingents were much more lightly armed ; the main weapon of the Achaemenid army historically was the bow and arrow , and javelin . Size of Macedonian army . Modern estimates . Alexander commanded a force from his kingdom of Macedon , Thracian allies , and the Corinthian League that — according to Arrian , the most reliable historian of Alexander ( who is believed to be relying on the work of the eye - witness Ptolemy ) – numbered 7 , 000 cavalry and 40 , 000 infantry . Most historians agree that the Macedonian army consisted of 31 , 000 heavy infantry , including the Greek hoplites in reserve , with an additional 9 , 000 light infantry consisting mainly of peltast s with some archer s . The size of the Macedonian mounted arm was about 7 , 000 . The battle . Initial dispositions . The battle began with the Persians already present at the battlefield . Darius had recruited the finest cavalry from his Eastern satrapies and from an allied Scythian tribe and deployed scythed chariot s , for which he had ordered bushes and vegetation removed from the battlefield to maximize their effectiveness . He also had 15 Indian elephants supported by Indian chariot s . Darius placed himself in the centre with his best infantry as was the tradition among Persian kings . He was surrounded by , on his right , the Carian cavalry , Greek mercenaries , and the Persian horse guards . In the right - center he placed the Persian foot guards ( Apple Bearers / Immortals to the Greeks ) , the Indian Cavalry and his Mardian archers . On both flanks were the cavalry . Bessus commanded the left flank with the Bactria ns , Dahae cavalry , Arachosia n cavalry , Persia n cavalry , Susian cavalry , Cadusian cavalry , and Scythians . Chariots were placed in front with a small group of Bactrians . Mazaeus commanded the right flank with the Syrian , Median , Mesopotamian , Parthian , Sacia n , Tapuria n , Hyrcania n , Caucasian Albania n , Sacesinia n , Cappadocian , and Armenia n cavalry . The Cappadocians and Armenians were stationed in front of the other cavalry units , and led the attack . The Albanian and Sacesinian cavalry were sent around to flank the Greek left . The Macedonian were divided into two , with the right side under the direct command of Alexander , and the left of Parmenion . Alexander fought with his Companion cavalry . With it were the Paionia n , and Greek light cavalry . The mercenary cavalry was divided into two groups , veterans on the flank of the right and the rest in front of the Agrians and Greek archers , which were stationed next to the phalanx . Parmenion was stationed on the left with the Thessalia ns , Greek mercenaries , and Thracia n cavalry . There they were to pull off a holding maneuver while Alexander landed the decisive blow from the right . On the right - centre were Cretan mercenaries . Behind them were Thessalian cavalry under Phillip , and Achaean mercenaries . To their right was another part of the allied Greek cavalry . From there came the phalanx , in a double line . Outnumbered over 5 : 1 in cavalry , with their line surpassed by over a mile , it seemed inevitable that the Greeks would be flanked by the Persians . The second line were given orders to deal with any flanking units should the situation arise . This second line consisted of mostly mercenaries . Beginning of the battle . Alexander began by ordering his infantry to march in phalanx formation towards the center of the enemy line . The Macedonian advanced with the wings echeloned back at 45 degrees to lure the Persian cavalry to attack . While the phalanxes battled the Persian infantry , Darius sent a large part of his cavalry and some of his regular infantry to attack Parmenion ' s forces on the left . During the battle Alexander used an unusual strategy which has been duplicated only a few times . While the infantry battled the Persian troops in the center , Alexander began to ride all the way to the edge of the right flank , accompanied by his Companion Cavalry . His plan was to draw as much of the Persian cavalry as possible to the flanks , to create a gap within the enemy line where a decisive blow could then be struck at Darius in the center . This required almost perfect timing and maneuvering , and Alexander himself to act first . Alexander would force Darius to attack ( as they would soon move off the prepared ground ) though Darius did not want to be the first to attack after seeing what happened at Issus against a similar formation . In the end Darius ' hand was forced , and he attacked . Mouse - trap tactic . Darius now launched his chariots , some of which were intercepted by the Agrianians ( javelin throwers ) . It is said that the Greek army had trained for a new tactic to counter these devastating chariots if they ran into their ranks : The first lines would step aside , opening a gap . The horse would refuse to run into the spears of the front ranks , and enter the " mouse trap " , to be stopped by the spears of the rear ranks . The charioteers and their horses could then be killed at leisure . Alexander ' s decisive attack . As the Persians advanced farther and farther to the Greek flanks in their attack , Alexander slowly filtered in his rearguard . Alexander disengaged his Companions , and prepared for the decisive attack . He formed his units into a giant wedge , with him leading the charge . Behind them were the guards brigade along with any phalanx battalions he could withdraw from the battle . These were follow - up light troops . Alexander took most of his cavalry and moved parallel to Darius ' s front lines , heading off of the prepared battlefield . In response , Darius ordered his cavalry in the front lines to block Alexander ' s force . Unknown to Darius , Alexander hid a force of peltasts ( light infantry armed with slings , javelins , and shortbows ) behind his horsemen and slowly sent his force into an angle , heading toward the Persian host , until finally a gap opened between Bessus ' s left and Darius ' s center and Alexander sent in his cavalry to drive down the gap in the Persian line in a wedge formation . At the same time , the peltasts engaged the cavalry in order to keep them from riding back to engage Alexander ' s charging cavalry . The Persian infantry at the center were still fighting the phalanxes , hindering any attempts to counter Alexander ' s charge . This large wedge then smashed into the weakened Persian center , taking out Darius ' s royal guard and the Greek mercenaries . Bessus on the left , cut off from Darius and fearing he would be struck with this wedge , began to pull back . Darius was in danger of being cut off , and the widely held modern view is that he now broke and ran , with the rest of his army following him . This is based on Arrian ' s account ( Anabasis 3 . 14 ) : A less common view is that Darius ' s army was already broken when Darius ran , and is supported by an astronomical diary from Babylon written within days of the battle : The left flank . Alexander could have pursued Darius at this point . However , he received desperate messages from Parmenion ( an event which would later be used by Callisthenes and others to discredit Parmenion ) on the left . Alexander was faced with the choice of pursuing Darius and having the chance of killing him , ending the war in one stroke , but risking losing his army , or going back to the left flank to aid Parmenion and preserve his forces , letting Darius escape to the surrounding mountains . He helped Parmenion , and followed Darius later . While holding on the left , a gap had opened up between the left and center of the Greek line . The Persian and Indian cavalry in the center with Darius broke through . Instead of taking the phalanx or Parmenion in the rear , they continued towards the camp to loot . They also tried to rescue the Queen Mother , Sisygambis , but she refused to go with them . Meanwhile , as the center and Darius broke , Mazaeus also began to pull his forces back as Bessus had . However , unlike on the left with Bessus , the Persians soon fell into disorder as the Thessalians and other cavalry units charged forward at their fleeing enemy . Aftermath . After the battle , Parmenion rounded up the Persian baggage train while Alexander and his bodyguard pursued Darius . As at Issus , substantial loot were gained , with 4 , 000 talents captured , the King ' s personal chariot and bow , and the war elephant s . It was a disastrous defeat for the Persians and one of Alexander ' s finest victories . Darius managed to escape with a small corps of his forces remaining intact . The Bactrian cavalry and Bessus caught up with him , as did some of the survivors of the Royal Guard and 2 , 000 Greek mercenaries . At this point , the Persian Empire was divided into two halves – East and West . On his escape , Darius gave a speech to what remained of his army . He planned to head further east and raise another army to face Alexander , assuming that the Macedonians would head towards Babylon . At the same time , he dispatched letters to his eastern satraps asking them to remain loyal . The satraps , however , had other intentions . Bessus murdered Darius before fleeing eastwards . When Alexander discovered Darius murdered , he was saddened to see an enemy he respected killed in such a fashion , and gave Darius a full burial ceremony at Persepolis , the former ceremonial capital of the Persian Empire , before angrily pursuing Bessus , capturing and executing him the following year . The majority of the remaining satraps gave their loyalty to Alexander and were allowed to keep their positions . The Persian Empire is traditionally considered to have ended with the death of Darius . In film . The Battle of Gaugamela is depicted in the film " Alexander " ( 2004 ) .