Siege of Patras ( 805 or 807 ) The Siege of Patras in 805 or 807 was undertaken by the local Slavic tribes of the Peloponnese , reportedly with aid from an Arab fleet . The siege ' s failure , attributed to the miraculous intervention of the city ' s patron , Saint Andrew , marked the consolidation of Byzantine control over the Peloponnese peninsula . It also marked the beginning of the ascendancy of the Metropolis of Patras in the peninsula ' s ecclesiastical affairs . Background . The Byzantine Empire ' s military position in the Balkans collapsed in the early 7th century as a result of disastrous military ventures against the Persians and then the Arabs in the East , which forced the effective abandonment of the Danube " limes " and opened the way for large - scale penetration of the Balkan hinterland by various Slavic tribes . The Slavs raided as far as southern Greece and the coasts of Asia Minor , and settled across the Balkan peninsula . Most of the region ' s cities were sacked or abandoned and only a few , including Thessalonica , remained occupied and in imperial hands . In Greece , the eastern coasts of the Peloponnese and Central Greece remained in Byzantine hands as the theme of Hellas , while in the interior , various Slavic groups established themselves . A large native Greek population probably also remained in the land , either mixed with the Slavs or in its own autonomous communities . As elsewhere in Greece , a mostly peaceful " modus vivendi " soon emerged between the Slavs and the remaining Byzantine strongholds , with the mainly agricultural Slavs trading with the Byzantine - held coastal towns . Further north , in the Greek mainland , by the turn of the 8th century smaller Slavic districts or " sclaviniae " emerged around the fringes of imperial territory , ruled by their own archon s , who received Byzantine titles and recognized some form of imperial suzerainty . Imperial authority across Greece was greatly strengthened by the 783 campaign of the logothete Staurakios , who ventured from Constantinople overland to Thessalonica and from there south to the Peloponnese , subduing the Slavs of those regions . Patras , on the northwestern coast of the Peloponnese , is claimed by the " Chronicle of Monemvasia " — a work of highly disputed accuracy and chronology , but an essential source for the period — to have been one of the cities abandoned circa 587 / 8 as a result of the Slavic depredations , its population fleeing to Rhegion in Calabria . This was followed by 218 years of independent Slavic rule in the Peloponnese , until around 804 / 5 . The archaeological record shows Patras to have remained in Byzantine control throughout the period , although it is possible that part of the population indeed emigrated to Italy . Siege of Patras . According to Chapter 49 of the " De administrando imperio " of Emperor Constantine VII Porphyrogennetos ( r . 913 – 959 ) , in the reign of Emperor Nikephoros I ( r . 802 – 811 ) the Slavs of the Peloponnese made war on the Greek population with the aid of " African Saracens " , looted the countryside and laid siege to Patras . The city held out for a while , but as food began growing short , the inhabitants gave thought to surrendering . First , however , they dispatched a rider to the direction of Corinth , the seat of the military governor ( " strategos " ) , to find out whether he was coming to their aid or not . The envoy had been instructed on his return to give a signal through a flag he carried : if help was on its way , he was to dip the flag , otherwise to hold it erect . The rider found out that the " strategos " was not coming or was delayed — Constantine VII writes that he arrived three days after the siege had ended — but on his return to the city , his horse slipped and both he and the flag fell down . The inhabitants of Patras interpreted this as a sign that aid was near , and sallied forth against the besieging Slavs , allegedly led by Saint Andrew himself on horseback . The Slavs panicked at the sudden assault and fled , abandoning the siege . As a punishment , Constantine VII records that the Slavs were thereafter obligated to maintain at their own cost all officials or envoys passing through Patras , relieving the metropolis of this burden . Constantine VII gives no precise date for the attack , but it has been usually dated to around 805 , when the city of Patras was " re - founded " according to the " Chronicle of Monemvasia " , or to 807 , when an Arab ( " Saracen " ) fleet reached southern Greece , although the Arab participation may well be the result of a later interpolation , mixing the real Slavic revolt with subsequent Arab raids . The " Chronicle of Monemvasia " on the other hand does not mention any siege of the city . Instead it records that an Armenian " strategos " at Corinth named Skleros defeated the Peloponnesian Slavs , and that this victory , in the year 804 / 5 or 805 / 6 , marked the end of 218 years of Slavic rule in the Peloponnese . Emperor Nikephoros I is then said to have rebuilt Patras by bringing back the descendants of its original inhabitants from Rhegion , and to have engaged in a large - scale resettlement and Christianization program for the peninsula , bringing in Greek colonists from Italy and Asia Minor . Nikephoros ' resettlement program at least is also confirmed by the chronicler Theophanes the Confessor , who puts it slightly later , in 810 / 811 . Some scholars have tried to reconcile the conflicting accounts of the " Chronicle " and the " De administrando imperio " as implying a first recovery of Patras circa 805 as the result of Skleros ' campaign , which was probably concurrent with the establishment of the Peloponnese as a separate theme from Hellas , if this had not been done slightly earlier . According to this interpretation , the Slavic revolt and attack on Patras followed as a reaction a few years later , between 807 and 811 . Aftermath . Whatever the exact course of events of the early 800s , the failure of the Slavic attack on Patras consolidated the recently re - established Byzantine control over the Peloponnese , and Nikephoros I ' s policies led to the successful re - Christianization and Hellenization of the peninsula . The defence of Patras also secured the Byzantine Empire ' s main maritime road of communication with Italy and the West , as it opened up the shorter route through the Corinthian Gulf , instead of the longer , more dangerous route around the Peloponnese that was exposed to Arab attacks . According to Constantine VII , the Slavs rose up again in the early 840s , but were defeated by " strategos " Theoktistos Bryennios . In the south , the two tribes of the Ezeritai and Melingoi held out longer . They were eventually subdued and forced to pay heavy tribute , but retained their autonomy . These two tribes rose up again a century later , in 921 . Again they were quickly subdued , this time by the " strategos " Krenites Arotras , but managed to remain autonomous and retain their distinct identity until well into Frankish times . The successful repulsion of the siege through the " intervention " of Saint Andrew also marked the abrupt rise of the see of Patras to prominence : formerly a suffragan of Corinth , it was raised to a separate metropolis and came to enjoy great political and financial influence . Henceforth the metropolitan of Patras rivalled with his former superior in Corinth over control of the other sees of the Peloponnese .