Byzantine Empire: Isaurian dynasty

Leo III the Isaurian was Byzantine Emperor from 717 until his death in 741 and founder of the Isaurian dynasty. He put an end to the Twenty Years' Anarchy, a period of great instability in the Byzantine Empire between 695 and 717, marked by the rapid succession of several emperors to the throne. He also successfully defended the Empire against the invading Umayyads and forbade the veneration of icons.

The second Arab siege of Constantinople in 717–718 was a combined land and sea offensive by the Muslim Arabs of the Umayyad Caliphate against the capital city of the Byzantine Empire, Constantinople. The campaign marked the culmination of twenty years of attacks and progressive Arab occupation of the Byzantine borderlands, while Byzantine strength was sapped by prolonged internal turmoil. In 716, after years of preparations, the Arabs, led by Maslama ibn Abd al-Malik, invaded Byzantine Asia Minor. The Arabs initially hoped to exploit Byzantine civil strife and made common cause with the general Leo III the Isaurian, who had risen up against Emperor Theodosius III. Leo, however, tricked them and secured the Byzantine throne for himself.

After wintering in the western coastlands of Asia Minor, the Arab army crossed into Thrace in early summer 717 and built siege lines to blockade the city, which was protected by the massive Theodosian Walls. The Arab fleet, which accompanied the land army and was meant to complete the city's blockade by sea, was neutralized soon after its arrival by the Byzantine navy through the use of Greek fire. This allowed Constantinople to be resupplied by sea, while the Arab army was crippled by famine and disease during the unusually hard winter that followed. In spring 718, two Arab fleets sent as reinforcements were destroyed by the Byzantines after their Christian crews defected, and an additional army sent overland through Asia Minor was ambushed and defeated. Coupled with attacks by the Bulgars on their rear, the Arabs were forced to lift the siege on 15 August 718. On its return journey, the Arab fleet was almost completely destroyed by natural disasters.

The siege's failure had wide-ranging repercussions. The rescue of Constantinople ensured the continued survival of Byzantium, while the Caliphate's strategic outlook was altered: although regular attacks on Byzantine territories continued, the goal of outright conquest was abandoned. Historians consider the siege to be one of history's most important battles, as its failure postponed the Muslim advance into Southeastern Europe for centuries.

In 719, former emperor Anastasius headed a revolt against Leo III, receiving considerable Bulgar support. The rebel forces advanced on Constantinople. The Bulgarians betrayed Anastasius, leading to his defeat. The enterprise failed, and Anastasius fell into Leo's hands and was put to death by his orders on 1 June. He was killed along with other conspirators including Niketas Xylinitas and the archbishop of Thessaloniki.

Leo undertook a set of civil reforms including the abolition of the system of prepaying taxes which had weighed heavily upon the wealthier proprietors, the elevation of the serfs into a class of free tenants and the remodelling of Family law, maritime law and criminal law, notably substituting mutilation for the death penalty in many cases. The new measures, which were embodied in a new code called the Ecloga (Selection), published in 726, met with some opposition on the part of the nobles and higher clergy. The Emperor also undertook some reorganization of the theme structure by creating new themata in the Aegean region.

Regular raids against the Byzantine Empire would continue in 727 up until 739. One regular commander of Arab forces was the redoubtable Maslama, Hisham's half-brother. He fought the Byzantines in 725–726 CE and the next year captured Caesarea Mazaca. 

Hisham's son Mu'awiya was another Arab commander in the almost-annual raids against the Byzantine Empire. In 728, he took the fort of Samalu in Cilicia. The next year Mu'awiya thrust left and Sa'id ibn Hisham right, in addition to a sea raid. In 731, Mu'awiya captured Kharsianon in Cappadocia.

Mu'awiya raided the Byzantine Empire in 731–732. The next year he captured Aqrun (Akroinos), while Abdallah al-Battal took a Byzantine commander prisoner. Mu'awiya raided Byzantium from 734–737. In 737, al Walid ibn al Qa'qa al-Absi led the raid against the Byzantines. The next year Sulayman ibn Hisham captured Sindira (Sideroun). In 738–739, Maslama captured some of Cappadocia and also raided the Avars.

Leo's frustration at his military failures led him to believe, in the fashion of the time, that the Empire had lost divine favour. Already in 722 he had tried to force the conversion of the Empire's Jews, but soon he began to turn his attention to the veneration of icons, which some bishops had come to regard as idolatrous. Following the renewed eruption of Thera in 726, he published an edict condemning their use, and had the image of Christ removed from the Chalke Gate, the ceremonial entrance to the Great Palace of Constantinople. The Emperor showed himself increasingly critical of the iconophiles, and in a court council in 730 he formally banned depictions of religious figures.

Leo's espousal of iconoclasm caused reactions among both the populace and the Church. The soldiers that took down the image of Christ from the Chalke were lynched, and a thematic rebellion that broke out in Greece in 727, was at least in part motivated by iconophile fervour. The Patriarch Germanos I resigned, to be replaced by the more pliant Anastasios. The emperor's edict drew the condemnation of popes Gregory II and Gregory III, as well as John of Damascus. Generally however, the dispute remained limited, as Leo refrained from actively persecuting iconophiles.

In the Italian Peninsula, the defiant attitude of Popes Gregory II and later Gregory III on behalf of image-veneration led to a fierce quarrel with the Emperor. The former summoned councils in Rome to anathematize and excommunicate the iconoclasts (730, 732); in 740 Leo retaliated by transferring Southern Italy and Illyricum from the papal diocese to that of the patriarch of Constantinople. The struggle was accompanied by an armed outbreak in the exarchate of Ravenna in 727, which Leo finally endeavoured to subdue by means of a large fleet. But the destruction of the armament by a storm decided the issue against him; his southern Italian subjects successfully defied his religious edicts, and the Exarchate of Ravenna became effectively detached from the Empire.

The Battle of Akroinon was fought on the western edge of the Anatolian plateau, in 740 between an Umayyad Arab army and the Byzantine forces. The Arabs had been conducting regular raids into Anatolia for the past century, and the 740 expedition was the largest in recent decades, consisting of three separate divisions. One division, 20,000 strong under Abdallah al-Battal and al-Malik ibn Shu'aib, was confronted at Akroinon by the Byzantines under the command of Emperor Leo III the Isaurian r. 717–741) and his son, the future Constantine V (r. 741–775). The battle resulted in a decisive Byzantine victory. Coupled with the Umayyad Caliphate's troubles on other fronts and the internal instability before and after the Abbasid Revolt, this put an end to major Arab incursions into Anatolia for three decades.

Akroinon was a major success for the Byzantines, as it was the first victory they had scored in a major pitched battle against the Arabs. Seeing it as evidence of God's renewed favour, the victory also served to strengthen Leo's belief in the policy of iconoclasm that he had adopted some years before. The Arab defeat at Akroinon has traditionally been seen as a decisive battle and a turning point of the Arab–Byzantine wars, causing the slackening of Arab pressure on Byzantium. Constantine V was able to take advantage of the Umayyad Caliphate's collapse to launch a series of expeditions into Syria and secure a Byzantine ascendancy on the eastern frontier which lasted until the 770s.

Constantine V's reign saw a consolidation of Byzantine security from external threats. As an able military leader, Constantine took advantage of civil war in the Muslim world to make limited offensives on the Arab frontier. With this eastern frontier secure, he undertook repeated campaigns against the Bulgars in the Balkans. His military activity, and policy of settling Christian populations from the Arab frontier in Thrace, made Byzantium's hold on its Balkan territories more secure.

Religious strife and controversy was a prominent feature of his reign. His fervent support of Iconoclasm and opposition to monasticism led to his vilification by later Byzantine historians and writers, who denigrated him as Kopronymos or Copronymus (Κοπρώνυμος), meaning the dung-named. The Byzantine Empire enjoyed a period of increasing internal prosperity during Constantine's reign. He was also responsible for important military and administrative innovations and reforms.

Constantine was crossing Asia Minor to campaign against the Umayyad Caliphate under Hisham ibn Abd al-Malik on the eastern frontier in June 741 or 742. But during this course Constantine was attacked by the forces of his brother-in-law Artabasdos, the stratēgos of the Armeniac theme. 

Defeated, Constantine sought refuge in Amorion, while the victor advanced on Constantinople and was accepted as emperor. While Constantine now received the support of the Anatolic and Thracesian themes, Artabasdos secured that of the themes of Thrace and Opsikion, in addition to his own Armeniac soldiers.

After the rival emperors had bided their time in military preparations, Artabasdos marched against Constantine, but was defeated in May 743 at Sardis. Three months later Constantine defeated Artabasdos' son Niketas and headed for Constantinople. In early November Constantine was admitted into the capital and immediately turned on his opponents, having them blinded or executed. Perhaps because Artabasdos' usurpation was interconnected with the restoration of veneration of images, Constantine now became perhaps an even more fervent iconoclast than his father.

In 746, profiting from the unstable conditions in the Umayyad Caliphate, which was falling apart under Marwan II, Byzantine emperor Constantine V conducts successful campaigns in northern Syria and Armenia, captured Germanikeia, and also thoroughly undermined Bulgarian strength. Coupled with military defeats on other fronts of the Caliphate and internal instability, Umayyad expansion came to an end.

There was a flare-up of bubonic plague between 746-749 CE – referred to as the Great Outbreak – in Constantinople, Greece, and Italy, with a death toll of upwards of 200,000, but in 750 CE the disease seemed to vanish

According to the sources, the Egyptian fleet sailed from Alexandria to Cyprus. The Byzantine strategos of the Cibyrrhaeots managed to surprise the Arabs and blockade the entrance of the harbour of Keramaia. As a result, almost the entire Arab fleet—Theophanes writes, with obvious exaggeration, of a thousand dromons, while Anastasius gives the more plausible number of thirty vessels—was destroyed. According to Theophanes, "it is said that only three ships escaped".

This crushing defeat was a signal event: in its aftermath, the Egyptian fleets are not mentioned until the second half of the 9th century, following the Sack of Damietta. Egypt ceased to be a major base for naval expeditions against Byzantium during the century after Keramaia.

Lombard king Aistulf captured Ravenna, ending over two centuries of Byzantine rule.

Constantine led an invasion into the new Abbasid Caliphate under As-Saffah. Constantine captured Theodosioupolis and Melitene (Malatya), and again resettled some of the population in the Balkans.

The iconoclast Council of Hieria was a Christian council of 754 which viewed itself as ecumenical, but was later rejected by the Second Council of Nicaea (787) and by Catholic and Orthodox churches, since none of the five major patriarchs were represented in Hieria.

The Council of Hieria was summoned by the Byzantine Emperor Constantine V in 754 in the palace of Hieria at Chalcedon. The council supported the emperor's iconoclast position in the Byzantine iconoclasm controversy, condemning the spiritual and liturgical use of iconography as heretical.

Opponents of the council described it as the Mock Synod of Constantinople or the Headless Council because no patriarchs or representatives of the five great patriarchates were present: the see of Constantinople was vacant; Antioch, Jerusalem and Alexandria were under Islamic dominion; while Rome was not asked to participate. Its rulings were anathematized at the Lateran Council of 769 before being overturned almost entirely by the Second Council of Nicaea in 787, which upheld the orthodoxy of and endorsed the veneration of holy images.

In 755, the long peace between Bulgaria and the Byzantine Empire came to an end. This was mainly because, after significant victories over the Arabs, the Byzantine Emperor Constantine V began to fortify his border with Bulgaria. To this aim he resettled heretics from Armenia and Syria in Thrace. Khan Kormisosh took those actions, and the construction of a new fortress along the border, as a breach of the Byzantine–Bulgarian Treaty of 716, signed by Tervel. The Bulgarian ruler sent envoys to ask for tribute for the new fortresses. After the refusal of the Byzantine Emperor, the Bulgarian army invaded Thrace. Looting everything on their way, the Bulgarians reached the outskirts of Constantinople, where they were engaged and defeated by Byzantine troops.

In the next year, Constantine V organized a large campaign against Bulgaria which was now ruled by a new khan, Vinekh. An army was sent with 500 ships which plundered the area around the Danube Delta. The Emperor himself, leading the main force, advanced into Thrace, and was engaged by the Bulgarians at the border castle of Marcellae. The details of the battle are unknown but it resulted in a victory for Constantine V. In order to stop the invasion, the Bulgarians sent hostages to Constantinople. 

Pepin III, after recovering Byzantine territories in Italy from the Lombards, hands control of the region to the pope in Rome. Rome turns towards the the Franks for protection.

The Donation of Pepin in 756 provided a legal basis for the creation of the Papal States, thus extending the temporal rule of the popes beyond the duchy of Rome. The treaty officially conferred upon the pope the territories belonging to Ravenna, even cities such as Forlì with their hinterlands, the Lombard conquests in the Romagna and in the Duchy of Spoleto and Benevento, and the Pentapolis (the "five cities" of Rimini, Pesaro, Fano, Senigallia and Ancona). Narni and Ceccano were former papal territories. The territories specified in the treaty of 756 had belonged to the Roman Empire. 

Envoys of the Empire met Pepin in Pavia and offered him a large sum of money to restore the lands to the Empire, but he refused, saying that they belonged to St Peter and the Roman church. This strip of territory extended diagonally across Italy from the Tyrrhenian to the Adriatic. 

Between 755 and 775, the Byzantine emperor Constantine V organised nine campaigns to eliminate Bulgaria and although he managed to defeat the Bulgarians several times, he never achieved his goal. In 759, the emperor led an army towards Bulgaria, but Khan Vinekh had enough time to bar several mountain passes. When the Byzantines reached the Rishki Pass they were ambushed and completely defeated. The Byzantine historian Theophanes the Confessor wrote that the Bulgarians killed the strategos of Thrace Leo, the commander of Drama, and many soldiers.

Khan Vinekh did not take the favourable opportunity to advance on enemy territory and sued for peace. This act was very unpopular among the nobles and the Khan was murdered in 761.

Constantine campaigned against the Slav tribes of Thrace and Macedonia in 762, deporting some tribes to the Opsician theme in Anatolia, though some voluntarily requested relocation away from the troubled Bulgarian border region. A contemporary Byzantine source reported that 208,000 Slavs emigrated from Bulgarian controlled areas into Byzantine territory and were settled in Anatolia.

After the success in the battle of the Rishki Pass (759) the Bulgarian Khan Vinekh showed surprising inaction and instead desired peace, which cost him the throne and his life. The new ruler, Telets, was a firm supporter for further military actions against the Byzantines. With his heavy cavalry he looted the border regions of the Byzantine Empire and on 16 June 763, Constantine V came out of Constantinople with a large army and a fleet of 800 ships, with 12 cavalrymen on each.

The energetic Bulgarian Khan barred the mountain passes and took advantageous positions on the heights near Anchialus, but his self-confidence and impatience incited him to go down to the lowlands and charge the enemy. The battle started at 10 in the morning and lasted until sunset. It was long and bloody, but in the end the Byzantines were victorious, although they lost many soldiers, nobles, and commanders. The Bulgarians also had heavy casualties and many were captured, while Telets managed to escape. Constantine V entered his capital in triumph and then killed the prisoners.

In 765 the Byzantines again successfully invaded Bulgaria, during this campaign both Constantine's candidate for the Bulgarian throne, Toktu, and his opponent, Pagan, were killed. Pagan was killed by his own slaves when he sought to evade his Bulgarian enemies by fleeing to Varna, where he wished to defect to the emperor. The cumulative effect of Constantine's repeated offensive campaigns and numerous victories caused considerable instability in Bulgaria, where six monarchs lost their crowns due to their failures in war against Byzantium.

When Constantine V died in September 775, while campaigning against the Bulgarians, Leo IV the Khazar became senior emperor on 14 September 775. In 778 Leo raided Abbasid Syria, decisively defeating the Abbasid army outside of Germanicia. Leo died on 8 September 780, of tuberculosis. He was succeeded by his underage son Constantine VI, with Irene serving as regent.

Leo launched an invasion against the Abbasids in 778, invading Syria with a force made up of the armies of the multiple themes, including: the Opsikion Theme, led by Gregory; the Anatolic Theme, led by Artabasdos; the Armeniac Theme, led by Karisterotzes; the Bucellarian Theme, led by Tatzates; and the Thracesian Theme, led by Lachanodrakon. Lachanodrakon besieged Germanicia for a time, before he was bribed to raise the siege, and then began to raid the surrounding countryside. The Abbasids attacked Lachanodrakon while he was raiding, but were decisively defeated by several Byzantine armies. The Byzantine generals who led troops during this battle were given a triumphal entry when they returned to Constantinople. The next year, in 779, Leo successfully repelled an attack by the Abbasids against Asia Minor.

Constantine VI was the only child of Emperor Leo IV and Irene. Constantine was crowned co-emperor by his father in 776, and succeeded as sole emperor at the age of nine under the regency of Irene in 780.

Empress Irene appointed Elpidius as governor (strategos) of the theme of Sicily. Soon after, however, on 15 April, Irene was informed that he had supported a plot, discovered in October of the previous year to depose her and elevate the Caesar Nikephoros, the eldest surviving son of Constantine V, to power. Irene immediately dispatched the spatharios Theophilos to Sicily to bring Elpidius back to Constantinople. Although his wife and children were left behind in Constantinople, Elpidius refused the summons and was supported by the people and the local army. It does not seem that Elpidius declared himself explicitly in revolt against Irene, but the Empress nevertheless had his wife and children publicly whipped and imprisoned in the capital's praetorium.

In autumn of 781 or early 782, Irene dispatched against him a large fleet under a trusted court eunuch, the patrikios Theodore. Elpidius's own military forces were meager, and after several battles he was defeated. Along with his lieutenant, the dux Nikephoros, he gathered what remained of the theme's treasury and fled to North Africa, where the Arab authorities welcomed him.

The Abbasid invasion of Asia Minor in 782 was one of the largest operations launched by the Abbasid Caliphate against the Byzantine Empire. The invasion was launched as a display of Abbasid military might in the aftermath of a series of Byzantine successes. Commanded by the Abbasid heir-apparent, the future Harun al-Rashid, the Abbasid army reached as far as Chrysopolis, across the Bosporus from the Byzantine capital, Constantinople, while secondary forces raided western Asia Minor and defeated the Byzantine forces there. As Harun did not intend to assault Constantinople and lacked ships to do so, he turned back.

The Byzantines, who in the meantime had neutralized the detachment left to secure the Abbasid army's rear in Phrygia, were able to trap Harun's army between their own converging forces. The defection of the Armenian general Tatzates, however, allowed Harun to regain the upper hand. The Abbasid prince sent for a truce and detained the high-ranking Byzantine envoys, who included Empress Irene's chief minister, Staurakios. This forced Irene to agree to a three-year truce and agree to pay an annual tribute of 70,000 or 90,000 dinars to the Abbasids. Irene then focused her attention to the Balkans, but warfare with the Arabs resumed in 786, until mounting Arab pressure led to another truce in 798, on terms similar to those of 782.

As early as 781, Irene began to seek a closer relationship with the Carolingian dynasty and the Papacy in Rome. She negotiated a marriage between her son Constantine and Rotrude, a daughter of Charlemagne by his third wife Hildegard. During this time Charlemagne was at war with the Saxons, and would later become the new king of the Franks. Irene went as far as to send an official to instruct the Frankish princess in Greek; however, Irene herself broke off the engagement in 787, against her son's wishes.

The Second Council of Nicaea met in CE 787 in Nicaea (site of the First Council of Nicaea; present-day İznik in Turkey) to restore the use and veneration of icons (or, holy images), which had been suppressed by imperial edict inside the Byzantine Empire during the reign of Leo III (717–741). His son, Constantine V (741–775), had held the Council of Hieria to make the suppression official.

In 787, Charlemagne directed his attention towards the Duchy of Benevento, where Arechis II was reigning independently with the self-given title of Princeps. Charlemagne's siege of Salerno forced Arechis into submission. However, after Arechis II's death in 787, his son Grimoald III proclaimed the Duchy of Benevento newly independent. Grimoald was attacked many times by Charles' or his sons' armies, without achieving a definitive victory. Charlemagne lost interest and never again returned to Southern Italy where Grimoald was able to keep the Duchy free from Frankish suzerainty.

In the last quarter of the 8th century Bulgaria overcame the internal political crisis after the end of the rule of the Dulo. The khans Telerig and Kardam managed to consolidate the central authority and put an end of the quarrels among the nobility. The Bulgarians finally had the opportunity to intensify their campaigns in Slavic-populated Macedonia. In 789 they penetrated deep into the valley of the Struma river and heavily defeated the Byzantines, killing the strategos of Thrace Filites. 

Due to the rugged terrain the advancing Byzantine army broke its order. Taking advantage of that mistake, Kardam ordered a counterattack which brought the Bulgarians a great success. The Bulgarian cavalry went round the Byzantines and cut their way back to their fortified camp and the fortress of Marcellae. The Bulgarians took the supplies, the treasury and the tent of the emperor. They chased Constantine VI to Constantinople, killing a great number of soldiers. Many Byzantine commanders and officers perished in the battle. After the defeat, Constantine VI had to conclude peace with Kardam and had to pay tribute. 

Rebellion of the Armeniacs against the restoration of Irene of Athens as co-ruler by Constantine VI. A movement developed in favor of Constantine VI's uncle, the Caesar Nikephoros. Constantine had his uncle's eyes put out and the tongues of his father's four other half-brothers cut off. His former Armenian supporters revolted after he had blinded their general Alexios Mosele. He crushed this revolt with extreme cruelty in 793.

Constantine VI divorced his wife Maria of Amnia, who had failed to provide him with a male heir, and married his mistress Theodote, an unpopular and canonically illegal act which sparked off the so-called "Moechian Controversy". Although the Patriarch Tarasios did not publicly speak against it, he did refuse to officiate the marriage. Popular disapproval was expressed by Theodote's uncle, Plato of Sakkoudion, who even broke communion with Tarasios for his passive stance. Plato's intransigence led to his own imprisonment, while his monastic supporters were persecuted and exiled to Thessalonica. The "Moechian Controversy" cost Constantine what popularity he had left, especially in the church establishment, which Irene took care to vocally support against her own son.

On 19 August 797 Constantine was captured, blinded, and imprisoned by the supporters of his mother, who had organized a conspiracy, leaving Irene to be crowned as first Empress regnant of Constantinople. It is unknown when exactly Constantine died; it was certainly before 805, though he may have died of his wounds shortly after being blinded. 

A member of the politically prominent Sarantapechos family, she was selected as Leo IV's bride for unknown reasons in 768. Even though her husband was an iconoclast, she harbored iconophile sympathies. During her rule as regent, she called the Second Council of Nicaea in 787, which condemned iconoclasm as heretical and brought an end to the first iconoclast period (730–787).

Pope Leo III—already seeking to break links with the Byzantine East—used Irene's alleged unprecedented status as a female ruler of the Roman Empire to proclaim Charlemagne emperor of the Holy Roman Empire on Christmas Day of 800 under the pretext that a woman could not rule and so the throne of the Roman Empire was actually vacant. For the first time in 300 years, there is an emperor of the "East" and an emperor of the "West".

In 802 the patricians conspired against her, deposing her on 31 October, and placing Nikephoros, the minister of finance on the throne. Irene was exiled to Lesbos and forced to support herself by spinning wool. She died the following year, on 9 August.