Battle of Lalakaon The Battle of Lalakaon ( ) or the Battle of Poson ( or Porson ) ( ) was fought in 863 between the Byzantine Empire and an invading Arab army in Paphlagonia ( modern northern Turkey ) . The Byzantine army was led by Petronas , the uncle of Emperor Michael III ( r . 842 – 867 ) , although Arab sources also mention the presence of Emperor Michael himself , while the Arabs were led by the emir of Melitene ( Malatya ) , Umar al - Aqta ( r . 830s – 863 ) . Umar al - Aqta was able to overcome the initial Byzantine resistance against his invasion and reach the shores of the Black Sea . The Byzantines then mobilized all their forces , and the Arab army was encircled near the River Lalakaon . The subsequent battle ended in a complete Byzantine victory and the death of the Emir on the field , and was followed by a successful Byzantine counteroffensive across the border . The Byzantine victories proved decisive : the main threats to the Byzantine borderlands were eliminated , and the era of Byzantine ascendancy in the East , which would culminate in the great conquests of the 10th century , had begun . The Byzantine success had another corollary : deliverance from constant Arab pressure on the eastern frontier allowed the Byzantine government to concentrate on affairs in Europe , and , in particular , neighboring Bulgaria . The Bulgarians were pressured into accepting the Byzantine form of Christianity , thus beginning this nation ' s absorption into the Byzantine cultural sphere . Background . Arab – Byzantine border wars . Following the rapid Muslim conquests of the 7th century , the Byzantine Empire found itself confined to Asia Minor , the southern coasts of the Balkans , and parts of Italy . As Byzantium remained the Caliphate ' s major infidel enemy , Arab raids ( " razzia s " ) into Asia Minor continued throughout the 8th and 9th centuries . Over time , these expeditions , launched from bases in the Arab frontier zone on an almost annual basis , acquired a quasi - ritualized character . During that period , the Byzantines were generally on the defensive , and suffered some catastrophic defeats such as the razing of Amorium , the home city of the reigning Byzantine dynasty , in 838 . Nevertheless , with the waning of the Abbasid Caliphate ' s power after 842 and the rise of semi - independent emirates along the Byzantine eastern frontier , the Byzantines were increasingly able to assert their own power . In the 850s , the most persistent threats to the Empire were the emirate of Melitene ( Malatya ) under Umar al - Aqta , the emirate of Tarsus under Ali ibn Yahya ( " Ali the Armenian " ) , the emirate of Qaliqala ( Theodosiopolis , modern Erzurum ) and the Paulicians of Tephrike under their leader Karbeas . Melitene , in particular , was a major threat to Byzantium as its location on the western side of the Anti - Taurus range allowed direct access to the Anatolian plateau . An indication of the threat posed by these states came in 860 , when their combined actions turned the year into a veritable " annus horribilis " for the Byzantines : Umar and Karbeas raided deep into Asia Minor and returned with much plunder ; they were followed shortly after by another raid by the forces of Tarsus under Ali , while a naval attack from Syria sacked the major Byzantine naval base at Attaleia . Arab invasion of 863 . In the summer of 863 , Umar struck again , joining forces with the Abbasid general Ja ' far ibn Dinar al - Khayyat ( probably the governor of Tarsus ) for a successful raid into Cappadocia . The Arabs crossed the Cilician Gates into Byzantine territory , plundering as they went , until they reached a place near Tyana . There , the Tarsian army returned home , but Umar obtained Ja ' far ' s leave to press on into Asia Minor . Umar ' s forces represented the bulk of his emirate ' s strength , but their size is unknown : the contemporary Muslim historian Ya ' qubi claims that Umar had 8 , 000 men at his disposal , while the Byzantine historians Genesius and Theophanes Continuatus inflate the numbers of the Arab army to 40 , 000 men . The Byzantinist John Haldon considers the former number to be closer to reality , and estimates the size of the " combined " Arab force at 15 , 000 – 20 , 000 men . It is likely that a Paulician contingent under Karbeas was present as well . On the Byzantine side , Emperor Michael III had assembled his army to counter the Arab raid , and met them at a battle in an area called Marj al - Usquf ( " Bishop ' s Meadow " ) by Arab sources , a highland near Malakopeia , north of Nazianzus . The battle was bloody with many casualties on both sides ; according to the Persian historian al - Tabari , only a thousand of Umar ' s army survived . Nevertheless , the Arabs managed to escape the Byzantines and continue their raid north into the Armeniac Theme , eventually reaching the Black Sea and sacking the port city of Amisos . The Byzantine historians report that Umar , enraged at the sea blocking his advance , ordered it to be lashed , but this is most likely inspired by the similar account of Xerxes during the Persian Wars . Battle . As soon as Michael learned of the fall of Amisos , he ordered a huge force to be assembled ( al - Tabari gives its size at 50 , 000 men ) under his uncle Petronas , the Domestic of the Schools , and Nasar , the " stratēgos " of the Bucellarian Theme . Al - Tabari records that the Emperor himself assumed command of these forces , but this is not supported by Byzantine sources . Given the bias against Michael by the historians writing during the Macedonian dynasty , this may be a deliberate omission . The forces assembled came from all over the Byzantine Empire . Three separate armies were formed and converged on the Arabs : a northern Byzantine force composed of the forces from the Black Sea themes of the Armeniacs , Bucellarians , Koloneia and Paphlagonia ; a southern force , probably the one that had already fought at the Bishop ' s Meadow and had kept shadowing the Arab army , composed from the Anatolic , Opsician and Cappadocian themes , as well as the " kleisourai " ( frontier districts ) of Seleukeia and Charsianon ; and the western force , under Petronas himself , comprising the men of the Macedonian , Thracian and Thracesian themes and of the imperial " tagmata " from the capital . The coordination of all these forces was not easy , but the Byzantine armies , marching from three directions , were able to converge on the same day ( September 2 ) and surround Umar ' s smaller army at a location called Poson ( Πόσων ) or Porson ( Πόρσων ) near the Lalakaon River . The exact location of the river and the battle site have not been identified , but most scholars agree that they lay near the river Halys , some southeast of Amisos . With the approach of the Byzantine armies , the only open escape route left to the Emir and his men was dominated by a strategically located hill . During the night , both Arabs and Byzantines endeavoured to occupy it , but the Byzantines emerged victorious from the ensuing fight . On the next day , September 3 , Umar decided to throw his entire force towards the west , where Petronas was located , attempting to achieve a breakthrough . The Byzantines though stood firm , giving the other two Byzantine wings time to close in and attack the Arab army ' s exposed rear and flanks . The rout was complete , as the larger part of the Arab army and Umar himself fell on the field . Casualties possibly included the Paulician leader Karbeas : although the latter ' s participation in the battle is uncertain , it is recorded that he died in that year . Only the Emir ' s son , at the head of a small force , managed to escape the battlefield , fleeing south towards the border area of Charsianon . He was , however , pursued by Machairas , the " kleisourarchēs " of Charsianon , and was defeated and captured with many of his men . Aftermath . The Byzantines moved quickly to take advantage of their victory : a Byzantine army invaded Arab - held Armenia , and sometime in October or November , defeated and killed the emir Ali ibn Yahya . Thus , within a single campaigning season , the Byzantines had eliminated the three most dangerous opponents on their eastern border . In retrospect , these successes proved decisive , as the battle permanently destroyed the power of Melitene . The Byzantine victory at Lalakaon altered the strategic balance in the region , and heralded the beginning of Byzantium ' s century - long offensive in the East . The importance of these victories did not go unnoticed at the time : the Byzantines hailed them as revenge for the sack of Amorium 25 years earlier , the victorious generals were granted a triumphal entry into Constantinople , and special celebrations and services were held . Petronas was awarded the high court title of " magistros " , and the " kleisoura " of Charsianon was raised to a full theme . The removal of the eastern threat and the rise of the Byzantines ' confidence also opened up opportunities in the west , where the Bulgarian ruler Boris ( r . 852 – 889 ) had been negotiating with the Pope and Louis the German ( r . 817 – 876 ) for a possible conversion of himself and his pagan people to Christianity . This expansion of Rome ' s ecclesiastic influence up to Constantinople ' s very doorstep could not be tolerated by the Byzantine government . In 864 , the victorious eastern armies were transferred to Europe and invaded Bulgaria , in a demonstration of military might that convinced Boris to accept Byzantine missionaries instead . Boris was baptized , taking the name Michael in honor of the Byzantine emperor , thus beginning the Christianization of Bulgaria and initiating the nation ' s absorption into the Byzantine - influenced , Eastern Orthodox world . Influence on heroic poetry . According to the French Byzantinist Henri Grégoire , the Byzantine success against the Arabs that culminated with the Battle of Lalakaon inspired the creation of one of the oldest surviving acritic ( heroic ) poems : the " Song of Armouris " . Grégoire claimed that the eponymous protagonist , the young Byzantine warrior Armouris , was actually inspired by Emperor Michael III . A battle from the Byzantine heroic cycle around Digenis Akritas also strongly recalls the events of Lalakaon , as the eponymous hero surrounds an Arab army near Malakopeia . Strong influences can be found in episodes in the Arab , and later Turkish , epic cycles around Battal Ghazi , as well as an episode in the " One Thousand and One Nights " .