Abbasid invasion of Asia Minor ( 806 ) The Abbasid invasion of Asia Minor in 806 was the largest operation ever launched by the Abbasid Caliphate against the Byzantine Empire . The expedition was commanded in person by the Abbasid Caliph Harun al - Rashid ( reign ed 786 – 809 ) , who wished to retaliate for the Byzantine successes in the Caliphate ' s frontier region in the previous year and impress Abbasid might upon the Byzantine emperor , Nikephoros I ( r . 802 – 811 ) . The huge Abbasid army , according to Arab sources numbering more than 135 , 000 men , raided across Cappadocia unopposed , capturing several towns and fortresses , most notably Herakleia , and forcing Nikephoros to seek peace in exchange for tribute . Following Harun ' s departure , however , Nikephoros violated the terms of the treaty and reoccupied the frontier forts he had been forced to abandon . Harun ' s preoccupation with a rebellion in Khurasan , and his death three years later , prohibited a reprisal on a similar scale . Moreover , the Abbasid civil war that began after 809 and the Byzantine preoccupation with the Bulgars contributed to a cessation of large - scale Arab – Byzantine conflict for two decades . Background . Following the deposition of Byzantine empress Irene of Athens in October 802 and the accession of Nikephoros I in her place , a more violent phase in the long history of the Arab – Byzantine Wars began . Following a series of destructive annual raids across Asia Minor by the Abbasid Caliphate , Irene seems to have secured a truce with the Caliph Harun al - Rashid in 798 in exchange for the annual payment of tribute , repeating the terms agreed for a three - year truce following Harun ' s first large - scale campaign in 782 . Nikephoros , on the other hand , was more warlike — a Syriac source records that when he learned of Nikephoros ' s accession , a Byzantine renegade warned the Arab governor of Upper Mesopotamia to " throw away his silk and put on his armour " . In addition , he was determined to refill the imperial treasury by , among other measures , ceasing the tribute . Harun retaliated at once , launching a raid under his son al - Qasim in spring 803 . Nikephoros could not respond to this , as he faced an ultimately unsuccessful revolt of the Byzantine army of Asia Minor under its commander - in - chief , Bardanes Tourkos . After disposing of Bardanes , Nikephoros assembled his army and marched out to meet a second , larger invasion under the Caliph himself . After Harun raided the frontier region , the two armies confronted one another for two months in central Asia Minor , but it did not come to a battle ; Nikephoros and Harun exchanged letters , until the Emperor arranged for a withdrawal and a truce for the remainder of the year in exchange for a one - off payment of tribute . In the next year , 804 , an Abbasid force under Ibrahim ibn Jibril crossed the Taurus Mountains into Asia Minor . Nikephoros set out to confront the Arabs , but was surprised and heavily defeated at the Battle of Krasos , where he barely escaped with his own life . Preoccupied with trouble in Khurasan , Harun now accepted tribute and made peace . An exchange of prisoners was also arranged and took place during the winter at the border of the two empires on the Lamos river in Cilicia : some 3 , 700 Muslims were exchanged for the Byzantines taken captive in the previous years . Harun then departed for Khurasan , leaving Qasim to watch over the Byzantine frontier . Nikephoros used the opportunity in the spring to rebuild the destroyed walls of the towns of Safsaf , Thebasa , and Ancyra , and that summer , he launched the first Byzantine raid in two decades , against the Arab frontier district ( " thughur " ) in Cilicia . The Byzantine army raided the territory surrounding the fortresses of Mopsuestia and Anazarbus and took prisoners as it went . The garrison of Mopsuestia attacked the Byzantine force and recovered most of the prisoners and spoils , but the Byzantines marched on to Tarsus . The city , which had been refortified and repopulated on Harun ' s orders in 786 to strengthen the Muslim hold on Cilicia , fell and the entire garrison was taken captive . At the same time , another Byzantine force raided the Upper Mesopotamia n " thughur " and unsuccessfully besieged the fortress of Melitene , while a Byzantine - instigated rebellion against the local Arab garrison began in Cyprus . This sudden resumption of Byzantine offensive activity greatly alarmed Harun . In addition , he received reports that Nikephoros was planning similar attacks for the next year , which this time would aim at the full reoccupation of these frontier territories . As the historian Warren Treadgold writes , if the Byzantines had been successful in this endeavour , " garrisoning Tarsus and Melitene would have partly blocked the main Arab invasion routes across the Taurus into the Byzantine heartland , to the Byzantines ' great benefit " . On the other hand , Nikephoros was certainly aware of the huge superiority of the Caliphate in men and resources , and probably intended this campaign simply as a show of strength and a test of his enemy ' s resolve . The campaign . Having settled matters in Khurasan , Harun returned to the west in November 805 and prepared a huge retaliatory expedition for 806 , drawing men from Syria , Palestine , Persia , and Egypt . According to al - Tabari , his army numbered 135 , 000 regular troops and additional volunteers and freebooters . These numbers — and the even more fantastic claims of the Byzantine chronicler Theophanes the Confessor of 300 , 000 men — are easily the largest ever recorded for the entire Abbasid era and far more than the estimated strength of the entire Byzantine army . Although they are certainly exaggerated , they are nevertheless indicative of the size of the Abbasid force . At the same time , a naval force under his admiral Humayd ibn Ma ' yuf al - Hajuri was prepared to raid Cyprus . The huge invasion army departed Harun ' s residence of Raqqa in northern Syria on 11 June 806 , with the Caliph at its head , allegedly wearing a cap with the inscription " Warrior for the Faith and Pilgrim " ( in Arabic , " " ghazi " , " hajj " " ) . The Abbasids crossed Cilicia , where Harun ordered Tarsus to be rebuilt , and entered Byzantine Cappadocia through the Cilician Gates . Harun marched to Tyana , which at the time seems to have been abandoned . There , he began to establish his base of operations , ordering ' Uqbah ibn Ja ' far al - Khuza ' i to refortify the town and erect a mosque . Harun ' s lieutenant Abdallah ibn Malik al - Khuza ' i took Sideropalos , from where Harun ' s cousin Dawud ibn ' Isa ibn Musa with half the Abbasid army , some 70 , 000 men according to al - Tabari , was sent to devastate Cappadocia . Another of Harun ' s generals , Sharahil ibn Ma ' n ibn Za ' ida captured the so - called " Fortress of the Slavs " ( " Hisn al - Saqalibah " ) and the recently rebuilt town of Thebasa , while Yazid ibn Makhlad captured the " Fort of the Willow " ( " al - Safsaf " ) and Malakopea . Andrasos was captured and Kyzistra was placed under siege , while raiders reached as far as Ancyra , which they did not capture . Harun himself with the other half of his forces went west and captured Herakleia after a month - long siege in August or September . The city was plundered and razed , and its inhabitants enslaved and deported to the Caliphate . At the same time , on Cyprus , Humayd ravaged the island and took some 16 , 000 Cypriots , including the archbishop , captive to Syria , where they were sold as slaves . Nikephoros , outnumbered and threatened by the Bulgars in his rear , could not resist the Abbasid onslaught . He campaigned himself at the head of his army and seemingly won a few minor engagements against isolated detachments , but stayed well clear of the main Abbasid forces . In the end , with the harrowing possibility of the Arabs wintering on Byzantine soil in Tyana , he sent three cleric s as ambassadors : Michael , the bishop of Synnada , Peter the abbot of the monastery of Goulaion , and Gregory , the steward of the metropolis of Amastris . Harun agreed to terms , which included an annual tribute ( 30 , 000 gold " nomismata " , according to Theophanes , 50 , 000 according to al - Tabari ) , but in addition , the Emperor and his son and heir , Staurakios , were to pay a humiliating personal poll - tax ( " jizya " ) of three gold coins each to the Caliph ( four and two respectively , in Tabari ' s version ) , thereby acknowledging themselves as the Caliph ' s subjects . In addition , Nikephoros promised not to rebuild the dismantled forts . Rashid then recalled his forces from their various sieges and evacuated Byzantine territory . Aftermath . The agreement of peace terms was followed by a surprisingly friendly exchange between the two rulers , related by al - Tabari : Nikephoros asked Harun to send him a girl from Herakleia , one of the candidate brides for his son Staurakios , and for some perfume . According to Tabari , Harun " ordered the slave girl to be sought out ; she was brought back , adorned with finery and installed on a seat in the tent in which he himself was lodging . The slave girl and the tent , together with its contents , vessels and fittings , were handed over to Nikephoros ' s envoy . He also sent to Nikephoros the perfume which he had requested , and he further sent to him dates , dishes of jellied sweets , raisins and healing drugs . " Nikephoros returned the favour by dispatching a horse laden with 50 , 000 silver coins , 100 satin garments , 200 garments of fine brocade , 12 falcons , four hunting dogs , and three more horses . But as soon as the Arabs had withdrawn , the Emperor again restored the frontier forts and thereafter ceased the payment of tribute . Theophanes records that Harun unexpectedly returned and seized Thebasa in retaliation , but this is not corroborated elsewhere . The Arabs did launch a series of retaliatory raids in the next year , but the spring raid under Yazid ibn Makhlad al - Hubayri al - Fazari was heavily defeated , with Yazid himself falling in the field . The larger summer raid under Harthama ibn A ' yan was met by Nikephoros in person , and after an indecisive battle both sides retreated . The Byzantines raided the region of Marash in return , while in late summer Humayd launched a major naval raid , which pillaged Rhodes and reached as far as the Peloponnese , where it fomented a rebellion among the local Slavs . On his return , however , Humayd lost several ships to a storm , and on the Peloponnese , the Slavic revolt was put down after failing to capture Patras . The failure of the year ' s Abbasid efforts was compounded by another revolt in Khurasan , which forced Harun to depart again for the East . The Caliph concluded a new truce , and another prisoner exchange was held at the Lamos in 808 . Nikephoros was thus left with his gains intact : both the restored frontier fortifications and the cessation of tribute . Impact . Harun ' s massive expedition achieved remarkably little in material terms . Despite the sack of Herakleia , which is given prominent treatment in Arab sources , no permanent result was achieved , as Nikephoros was quick to violate the terms of the truce . If Harun had taken the advice offered by some of his lieutenants and proceeded further west to sack major cities , he could have inflicted long - lasting damage on Byzantium . As it was , the Caliph was content with a show of force that would intimidate Nikephoros and prevent him from repeating the offensive of 805 . In this regard , the Abbasid campaign was certainly a success : after 806 , the Byzantine ruler abandoned whatever expansionist plans he may have had for the eastern border and focused his energy on his fiscal reforms , the recovery of the Balkans , and his wars there against the Bulgars . Nikephoros ' s efforts would end tragically in the disastrous Battle of Pliska in 811 , but following Harun ' s death on 24 March 809 , the Caliphate was riven by a civil war between his sons al - Amin ( r . 809 – 813 ) and al - Ma ' mun ( r . 813 – 833 ) , and was not able to exploit the Byzantine reversals . Indeed , the 806 campaign and the ineffectual raids of 807 mark the last major , centrally organized , Abbasid expeditions against Byzantium for over twenty years . Only after the accession of Theophilos ( r . 829 – 842 ) and his confrontations with al - Ma ' mun and al - Mu ' tasim ( r . 833 – 842 ) would large - scale cross - border operations between the two empires resume . The longest - lasting impact of Harun ' s campaign is found in literature . Among the Arabs , several legends , related by al - Masudi , were associated with it . The Ottoman Turks also placed great importance on Harun ' s battles with the Byzantines . Influenced by the events of Harun ' s 782 campaign , Evliya Çelebi has the Caliph besieging Constantinople twice : the first time Harun withdrew , after securing as much land as an oxhide could cover and building a fortress there ( an imitation of the tale of Queen Dido ) and in the second Harun had Nikephoros hanged from the Hagia Sophia .