As the historiographical periodizations of "Roman history", "late antiquity", and "Byzantine history" significantly overlap, there is no consensus on a "foundation date" for the Byzantine Empire, if there was one at all. The growth of the study of "late antiquity" has led to some historians setting a start date in the seventh or eighth centuries.^[6] Others believe a "new empire" began during changes in c. 300 AD.^[7] Still others hold that these starting points are too early or too late, and instead begin c. 500.^[8] Geoffrey Greatrex believes that it is impossible to precisely date the foundation of the Byzantine Empire.^[9]

Early history (pre-518)

In a series of conflicts between the third and first centuries BC, the Roman Republic gradually established hegemony over the eastern Mediterranean, while its government ultimately transformed into the one-person rule of an emperor. The Roman Empire enjoyed a period of relative stability until the third century AD, when a combination of external threats and internal instabilities caused the Roman state to splinter as regional armies acclaimed their generals as "soldier-emperors".^[10] One of these, Diocletian (r. 284–305), seeing that the state was too big to be ruled by one man, attempted to fix the problem by instituting a Tetrarchy, or rule of four, and dividing the empire into eastern and western halves. Although the Tetrarchy system quickly failed, the division of the empire proved an enduring concept.^[11]

Constantine I (r. 306–337) secured sole power in 324. Over the following six years, he rebuilt the city of Byzantium as a capital city, which was renamed Constantinople. Rome, the previous capital, was further from the important eastern provinces and in a less strategically important location; it was not esteemed by the "soldier-emperors" who ruled from the frontiers or by the empire's population who, having been granted citizenship, considered themselves "Roman".^[12] Constantine extensively reformed the empire's military and civil administration and instituted the gold solidus as a stable currency.^[13] He favoured Christianity, which he had converted to in 312.^[14] Constantine's dynasty fought a lengthy conflict against Sasanid Persia and ended in 363 with the death of his son-in-law Julian.^[15] The short Valentinianic dynasty, occupied with wars against barbarians, religious debates, and anti-corruption campaigns, ended in the East with the death of Valens at the Battle of Adrianople in 378.^[16]

Thumb — Division of the empire after the death of Theodosius I in 395.
The Western Roman Empire

The Byzantine/Eastern Roman Empire

Valens's successor, Theodosius I (r. 379–395), restored political stability in the east by allowing the Goths to settle in Roman territory;^[17] he also twice intervened in the western half, defeating the usurpers Magnus Maximus and Eugenius in 388 and 394 respectively.^[18] He actively condemned paganism, confirmed the primacy of Nicene Christianity over Arianism, and established Christianity as the Roman state religion.^[19] He was the last emperor to rule both the western and eastern halves of the empire;^[20] after his death, the West would be destabilised by a succession of "soldier-emperors", unlike the East, where administrators would continue to hold power. Theodosius II (r. 408–450) largely left the rule of the east to officials such as Anthemius, who constructed the Theodosian Walls to defend Constantinople, now firmly entrenched as Rome's capital.^[21]

Theodosius' reign was marked by the theological dispute over Nestorianism, which was eventually deemed heretical, and by the formulation of the Codex Theodosianus law code.^[22] It also saw the arrival of Attila's Huns, who ravaged the Balkans and exacted a massive tribute from the empire; Attilla however switched his attention to the rapidly-deteriorating western empire, and his people fractured after his death in 453.^[23] After Leo I (r. 457–474) failed in his 468 attempt to reconquer the west, the warlord Odoacer deposed Romulus Augustulus in 476, killed his titular successor Julius Nepos in 480, and the office of western emperor was formally abolished.^[24]

Through a combination of luck, cultural factors, and political decisions, the Eastern empire never suffered from rebellious barbarian vassals and was never ruled by barbarian warlords—the problems which ensured the downfall of the West.^[25] Zeno (r. 474–491) convinced the problematic Ostrogoth king Theodoric to take control of Italy from Odoacer, which he did; dying with the empire at peace, Zeno was succeeded by Anastasius I (r. 491–518).^[26] Although his Monophysitism brought occasional issues, Anastasius was a capable administrator and instituted several successful financial reforms including the abolition of the chrysargyron tax. He was the first emperor to die with no serious problems affecting his empire since Diocletian.^[27]

518–717

Emperor Justinian (left), and the general Belisarius (right). Mosaics, 6th century, from the Basilica of San Vitale, Ravenna, Italy

The reign of Justinian I was a watershed in Byzantine history.^[28] Following his accession in 527, the law-code was rewritten as the influential Corpus Juris Civilis and Justinian produced extensive legislation on provincial administration;^[29] he reasserted imperial control over religion and morality through purges of non-Christians and "deviants";^[30] and having ruthlessly subdued the 532 Nika revolt he rebuilt much of Constantinople, including the original Hagia Sophia.^[31] Justinian took advantage of political instability in Italy to attempt the reconquest of lost western territories. The Vandal Kingdom in North Africa was subjugated in 534 by the general Belisarius, who then invaded Italy; the Ostrogothic Kingdom was destroyed in 554.^[32]

In the 540s, however, Justinian began to suffer reversals on multiple fronts. Taking advantage of Constantinople's preoccupation with the West, Khosrow I of the Sasanian Empire invaded Byzantine territory and sacked Antioch in 540.^[33] Meanwhile, the emperor's internal reforms and policies began to falter, not helped by a devastating plague that killed a large proportion of the population and severely weakened the empire's social and financial stability.^[34] The most difficult period of the Ostrogothic war, against their king Totila, came during this decade, while divisions among Justinian's advisors undercut the administration's response.^[35] He also did not fully heal the divisions in Chalcedonian Christianity, as the Second Council of Constantinople failed to make a real difference.^[36] Justinian died in 565; his reign saw more success than that of any other Byzantine emperor, yet he left his empire under massive strain.^[37]

Financially and territorially overextended, Justin II (r. 565–578) was soon at war on many fronts. The Lombards, fearing the aggressive Avars, conquered much of northern Italy by 572.^[38] The Sasanian wars restarted that year, and continued until the emperor Maurice finally emerged victorious in 591; by that time, the Avars and Slavs had repeatedly invaded the Balkans, causing great instability.^[39] Maurice campaigned extensively in the region during the 590s, but although he managed to re-establish Byzantine control up to the Danube, he pushed his troops too far in 602—they mutinied, proclaimed an officer named Phocas as emperor, and executed Maurice.^[40] The Sasanians seized their moment and reopened hostilities; Phocas was unable to cope and soon faced a major rebellion led by Heraclius. Phocas lost Constantinople in 610 and was soon executed, but the destructive civil war accelerated the empire's decline.^[41]

Top: the Sasanian Empire at its territorial apex under Khosrow II
Bottom: the Theodosian Walls of Constantinople, critically important during the 717–718 siege.

Under Khosrow II, the Sassanids occupied the Levant and Egypt and pushed into Asia Minor, while Byzantine control of Italy slipped and the Avars and Slavs ran riot in the Balkans.^[42] Although Heraclius repelled a siege of Constantinople in 626 and defeated the Sassanids in 627, this was a pyrrhic victory.^[43] The early Muslim conquests soon saw the conquest of the Levant, of Egypt, and of the Sassanid Empire by the newly-formed Arabic Rashidun Caliphate.^[44] By Heraclius' death in 641, the empire had been severely reduced economically as well as territorially—the loss of the wealthy eastern provinces had deprived Constantinople of three-quarters of its revenue.^[45]

The next seventy-five years are poorly documented.^[46] Arab raids into Asia Minor began almost immediately, and the Byzantines resorted to holding fortified centres and avoiding battle at all costs; although it was invaded annually, Anatolia avoided permanent Arab occupation.^[47] The outbreak of the First Fitna in 656 gave Byzantium breathing space, which it used wisely: some order was restored in the Balkans by Constans II (r. 641–668),^[48] who began the administrative reorganisation known as the "theme system", in which troops were allocated to defend specific provinces.^[49] With the help of the recently rediscovered Greek fire, Constantine IV (r. 668–685) repelled the Arab efforts to capture Constantinople in the 670s,^[50] but suffered a reversal against the Bulgars, who soon established an empire in the northern Balkans.^[51] Nevertheless, he and Constans had done enough to secure the empire's position, especially as the Umayyad Caliphate was undergoing another civil war.^[52]

Justinian II sought to build on the stability secured by his father Constantine but was overthrown in 695 after attempting to exact too much from his subjects; over the next twenty-two years, six more rebellions followed in an era of political instability.^[53] The reconstituted caliphate sought to break Byzantium by taking Constantinople, but the newly crowned Leo III managed to repel the 717–718 siege, the first major setback of the Muslim conquests.^[54]

718–867

Leo and his son Constantine V (r. 741–775), two of the most capable Byzantine emperors, withstood continued Arab attacks, civil unrest, and natural disasters, and reestablished the state as a major regional power.^[55] Leo's reign produced the Ecloga, a new code of law to succeed that of Justinian II,^[56] and continued to reform the "theme system" in order to lead offensive campaigns against the Muslims, culminating in a decisive victory in 740.^[57] Constantine overcame an early civil war against his brother-in-law Artabasdos, made peace with the new Abbasid Caliphate, campaigned successfully against the Bulgars, and continued to make administrative and military reforms.^[58] However, due to both emperors' support for the Byzantine Iconoclasm, which opposed the use of religious icons, they were later vilified by Byzantine historians;^[59] Constantine's reign also saw the loss of Ravenna to the Lombards, and the beginning of a split with the Roman papacy.^[60]

In 780, Empress Irene assumed power on behalf of her son Constantine VI.^[61] Although she was a capable administrator who temporarily resolved the iconoclasm controversy,^[62] the empire was destabilized by her feud with her son. The Bulgars and Abbasids meanwhile inflicted numerous defeats on the Byzantine armies, and the papacy crowned Charlemagne as Roman emperor in 800.^[63] In 802, the unpopular Irene was overthrown by Nikephoros I; he reformed the empire's administration but died in battle against the Bulgars in 811.^[64] Military defeats and societal disorder, especially the resurgence of iconoclasm, characterised the next eighteen years.^[65]

Stability was somewhat restored during the reign of Theophilos (r. 829–842), who exploited economic growth to complete construction programs, including rebuilding the sea walls of Constantinople, overhaul provincial governance, and wage inconclusive campaigns against the Abbasids.^[66] After his death, his empress Theodora, ruling on behalf of her son Michael III, permanently extinguished the iconoclastic movement;^[67] the empire prospered under their sometimes-fraught rule. However, Michael was posthumously vilified by historians loyal to the dynasty of his successor Basil I, who assassinated him in 867 and who was given credit for his predecessor's achievements.^[68]

867–1081

Basil I (r. 867–886) continued Michael's policies.^[69] His armies campaigned with mixed results in Italy but defeated the Paulicians of Tephrike.^[70] His successor Leo VI (r. 886–912)^{[lower-alpha 2]} compiled and propagated a huge number of written works. These included the Basilika, a Greek translation of Justinian I's law-code which included over 100 new laws of Leo's devising; the Tactica, a military treatise; and the Book of the Eparch, which codified Constantinople's trading regulations.^[72] In non-literary contexts Leo was less successful: the empire lost in Sicily and against the Bulgarians,^[73] while he provoked theological scandal by marrying four times in an attempt to father a legitimate heir.^[74]

The early reign of Leo's young heir, Constantine VII, was tumultuous, as his mother Zoe, the patriarch Nicholas, the powerful Simeon I of Bulgaria, and other influential figures jockeyed for power.^[75] In 920, the admiral Romanos I used his fleet to secure power, crowning himself and demoting Constantine to the position of junior co-emperor.^[76]

Between 1021 and 1022, following years of tensions, Basil II led a series of victorious campaigns against the Kingdom of Georgia, resulting in the annexation of several Georgian provinces to the empire. Basil's successors also annexed Bagratid Armenia in 1045. Importantly, both Georgia and Armenia were significantly weakened by the Byzantine administration's policy of heavy taxation and abolishing of the levy. The weakening of Georgia and Armenia played a significant role in the Byzantine defeat at Manzikert in 1071.^[77]

Basil II is considered among the most capable Byzantine emperors and his reign as the apex of the empire in the Middle Ages. By 1025, the date of Basil II's death, the Byzantine Empire stretched from Armenia in the east to Calabria in southern Italy in the west.^[78] Many successes had been achieved, ranging from the conquest of Bulgaria to the annexation of parts of Georgia and Armenia, and the reconquests of Crete, Cyprus, and the important city of Antioch. These were not temporary tactical gains but long-term reconquests.^[79]

The Byzantine Empire then fell into a period of difficulties, caused to a large extent by the undermining of the theme system and the neglect of the military. Nikephoros II, John Tzimiskes, and Basil II shifted the emphasis of the military divisions (τάγματα, tagmata) from a reactive, defence-oriented citizen army into an army of professional career soldiers, increasingly dependent on foreign mercenaries. Mercenaries were expensive, however, and as the threat of invasion receded in the 10th century, so did the need for maintaining large garrisons and expensive fortifications.^[80] Basil II left a burgeoning treasury upon his death, but he neglected to plan for his succession. None of his immediate successors had any particular military or political talent, and the imperial administration increasingly fell into the hands of the civil service. Incompetent efforts to revive the Byzantine economy resulted in severe inflation and a debased gold currency. The army was seen as both an unnecessary expense and a political threat. Several standing local units were demobilised, further augmenting the army's dependence on mercenaries, who could be retained and dismissed on an as-needed basis.^[81]

At the same time, Byzantium was faced with new enemies. Its provinces in southern Italy were threatened by the Normans who arrived in Italy at the beginning of the 11th century. During a period of strife between Constantinople and Rome culminating in the East-West Schism of 1054, the Normans advanced gradually into Byzantine Italy.^[82] Reggio, the capital of the tagma of Calabria, was captured in 1060 by Robert Guiscard, followed by Otranto in 1068. Bari, the main Byzantine stronghold in Apulia, was besieged in August 1068 and fell in April 1071.^[83]

About 1053, Constantine IX disbanded what the historian John Skylitzes calls the "Iberian Army", which consisted of 50,000 men, and it was turned into a contemporary Drungary of the Watch. Two other knowledgeable contemporaries, the former officials Michael Attaleiates and Kekaumenos, agree with Skylitzes that by demobilising these soldiers, Constantine did catastrophic harm to the empire's eastern defences. The emergency lent weight to the military aristocracy in Anatolia, who in 1068 secured the election of one of their own, Romanos Diogenes, as emperor. In the summer of 1071, Romanos undertook a massive eastern campaign to draw the Seljuks into a general engagement with the Byzantine army. At the Battle of Manzikert, Romanos suffered a surprise defeat against Sultan Alp Arslan and was captured. Alp Arslan treated him with respect and imposed no harsh terms on the Byzantines.^[81] In Constantinople a coup put in power Michael Doukas, who soon faced the opposition of Nikephoros Bryennios and Nikephoros III Botaneiates. By 1081, the Seljuks had expanded their rule over virtually the entire Anatolian plateau from Armenia in the east to Bithynia in the west, and had established their capital at Nicaea, just 90 kilometres (56 miles) from Constantinople.^[84]

Komnenian dynasty and the Crusades

Alexios I and the First Crusade

The Komnenian dynasty attained full power under Alexios I in 1081. From the outset of his reign, Alexios faced a formidable attack from the Normans under Guiscard and his son Bohemund of Taranto, who captured Dyrrhachium and Corfu and laid siege to Larissa in Thessaly. Guiscard's death in 1085 temporarily eased the Norman problem. The following year, the Seljuq sultan died, and the sultanate was split due to internal rivalries. By his own efforts, Alexios defeated the Pechenegs, who were caught by surprise and annihilated at the Battle of Levounion on 28 April 1091.^[85]

Thumb — The Byzantine Empire and the Seljuk Sultanate of Rûm before the First Crusade (1095–1099)

Having achieved stability in the West, Alexios could turn his attention to the severe economic difficulties and the disintegration of the empire's traditional defences.^[86] However, he still did not have enough manpower to recover the lost territories in Asia Minor and to the advance by the Seljuks. At the Council of Piacenza in 1095, envoys from Alexios spoke to Pope Urban II about the suffering of the Christians of the East and underscored that without help from the West, they would continue to suffer under Muslim rule. Urban saw Alexios' request as a dual opportunity to cement Western Europe and reunite the Eastern Orthodox Church with the Roman Catholic Church under his rule.^[87] On 27 November 1095, Urban called the Council of Clermont and urged all those present to take up arms under the sign of the Cross and launch an armed pilgrimage to recover Jerusalem and the East from the Muslims. The response in Western Europe was overwhelming.^[85] Alexios was able to recover a number of important cities, islands and much of western Asia Minor. The Crusaders agreed to become Alexios' vassals under the Treaty of Devol in 1108, which marked the end of the Norman threat during Alexios' reign.^[88]^[89]

John II, Manuel I, and the Second Crusade

Alexios's son John II Komnenos succeeded him in 1118 and ruled until 1143. John was a pious and dedicated emperor who was determined to undo the damage to the empire suffered at the Battle of Manzikert half a century earlier.^[90] Famed for his piety and his remarkably mild and just reign, John was an exceptional example of a moral ruler at a time when cruelty was the norm.^[91] For this reason, he has been called the Byzantine Marcus Aurelius. During his twenty-five-year reign, John made alliances with the Holy Roman Empire in the West and decisively defeated the Pechenegs at the Battle of Beroia.^[92] He thwarted Hungarian and Serbian threats during the 1120s, and in 1130 he allied himself with Lothair III, the German Emperor against the Norman King Roger II of Sicily.^[93]

In the later part of his reign, John focused his activities on the East, personally leading numerous campaigns against the Turks in Asia Minor. His campaigns fundamentally altered the balance of power in the East, forcing the Turks onto the defensive, while retaking many towns, fortresses, and cities across the peninsula for the Byzantines. He defeated the Danishmend Emirate of Melitene and reconquered all of Cilicia,^[94] while forcing Raymond of Poitiers, Prince of Antioch, to recognise Byzantine suzerainty.^[95] In an effort to demonstrate the emperor's role as the leader of the Christian world, John marched into the Holy Land at the head of the combined forces of the empire and the Crusader states; yet despite his efforts in leading the campaign, his hopes were disappointed by the treachery of his Crusader allies.^[96] In 1142, John returned to press his claims to Antioch, but he died in the spring of 1143 following a hunting accident.^[97]

John's chosen heir was his fourth son, Manuel I Komnenos, who campaigned aggressively against his neighbours both in the west and east. In Palestine, Manuel allied with the Crusader Kingdom of Jerusalem and sent a large fleet to participate in a combined invasion of Fatimid Egypt. Manuel reinforced his position as overlord of the Crusader states, with his hegemony over Antioch and Jerusalem secured by agreement with Raynald, Prince of Antioch, and Amalric of Jerusalem.^[98] In an effort to restore Byzantine control over the ports of southern Italy, he sent an expedition to Italy in 1155, but disputes within the coalition led to the eventual failure of the campaign. Despite this military setback, Manuel's armies successfully invaded the southern parts of the Kingdom of Hungary in 1167, defeating the Hungarians at the Battle of Sirmium. By 1168, nearly the whole of the eastern Adriatic coast lay in Manuel's hands.^[99] Manuel made several alliances with the pope and Western Christian kingdoms, and he successfully handled the passage of the crusaders through his empire.^[100]

In the East, Manuel suffered a major defeat in 1176 at the Battle of Myriokephalon against the Turks. These losses were quickly recovered, and in the following year Manuel's forces inflicted a defeat upon a force of "picked Turks".^[101] The Byzantine commander John Vatatzes, who destroyed the Turkish invaders at the Battle of Hyelion and Leimocheir, brought troops from the capital and was able to gather an army along the way, a sign that the Byzantine army remained strong and that the defensive program of western Asia Minor was still successful.^[102] John and Manuel pursued active military policies, and both deployed considerable resources on sieges and city defences; aggressive fortification policies were at the heart of their imperial military policies.^[103] Despite the defeat at Myriokephalon, the policies of Alexios, John and Manuel resulted in vast territorial gains, increased frontier stability in Asia Minor, and secured the stabilisation of the empire's European frontiers. From c. 1081 to c. 1180, the Komnenian army assured the empire's security, enabling Byzantine civilisation to flourish.^[104]

This allowed the Western provinces to achieve an economic revival that continued until the close of the century. It has been argued that Byzantium under the Komnenian rule was more prosperous than at any time since the Persian invasions of the 7th century. During the 12th century, population levels rose and extensive tracts of new agricultural land were brought into production. Archaeological evidence from both Europe and Asia Minor shows a considerable increase in the size of urban settlements, together with a notable upsurge in new towns. Trade was also flourishing; the Venetians, the Genoese and others opened up the ports of the Aegean to commerce, shipping goods from the Crusader states and Fatimid Egypt to the west and trading with the empire via Constantinople.^[105]

Decline and disintegration

Angelid dynasty

Manuel's death on 24 September 1180 left his 11-year-old son Alexios II Komnenos on the throne. Alexios was highly incompetent in the office, and with his mother Maria of Antioch's Frankish background, his regency was unpopular.^[106] Eventually, Andronikos I Komnenos, a grandson of Alexios I, overthrew Alexios II in a violent coup d'état. After eliminating his potential rivals, he had himself crowned as co-emperor in September 1183. He eliminated Alexios II and took his 12-year-old wife Agnes of France for himself.^[107]

Andronikos began his reign well; in particular, the measures he took to reform the government of the empire have been praised by historians. According to the historian George Ostrogorsky, Andronikos was determined to root out corruption: under his rule, the sale of offices ceased; selection was based on merit, rather than favouritism; and officials were paid an adequate salary to reduce the temptation of bribery. In the provinces, Andronikos's reforms produced a speedy and marked improvement.^[108] Gradually, however, Andronikos's reign deteriorated. The aristocrats were infuriated against him, and to make matters worse, Andronikos seemed to have become increasingly unbalanced; executions and violence became increasingly common, and his reign turned into a reign of terror.^[109] Andronikos seemed almost to seek the extermination of the aristocracy as a whole. The struggle against the aristocracy turned into wholesale slaughter, while the emperor resorted to ever more ruthless measures to shore up his regime.^[108]

Despite his military background, Andronikos failed to deal with Isaac Komnenos of Cyprus, Béla III of Hungary who reincorporated Croatian territories into Hungary, and Stephen Nemanja of Serbia who declared his independence from the Byzantine Empire. Yet, none of these troubles compared to William II of Sicily's invasion force of 300 ships and 80,000 men, arriving in 1185 and sacking Thessalonica.^[110] Andronikos mobilised a small fleet of 100 ships to defend the capital, but other than that he was indifferent to the populace. He was finally overthrown when Isaac II Angelos, surviving an imperial assassination attempt, seized power with the aid of the people and had Andronikos killed.^[111]

The reign of Isaac II, and more so that of his brother Alexios III, saw the collapse of what remained of the centralised machinery of Byzantine government and defence. Although the Normans were driven out of Greece, in 1186 the Vlachs and Bulgars began a rebellion that led to the formation of the Second Bulgarian Empire. The internal policy of the Angeloi was characterised by the squandering of the public treasure and fiscal maladministration. Imperial authority was severely weakened, and the growing power vacuum at the centre of the empire encouraged fragmentation. There is evidence that some Komnenian heirs had set up a semi-independent state in Trebizond before 1204.^[112] According to Alexander Vasiliev, "the dynasty of the Angeloi, Greek in its origin, ... accelerated the ruin of the Empire, already weakened without and disunited within."^[113]

Fourth Crusade and aftermath

In 1198, Pope Innocent III broached the subject of a new crusade through legates and encyclical letters.^[114] The stated intent of the crusade was to conquer Egypt, the centre of Muslim power in the Levant. The Crusader army arrived at Venice in the summer of 1202 and hired the Venetian fleet to transport them to Egypt. As a payment to the Venetians, they captured the (Christian) port of Zara in Dalmatia, which was a vassal city of Venice, it had rebelled and placed itself under Hungary's protection in 1186.^[115] Shortly afterward, Alexios IV Angelos, son of the deposed and blinded Emperor Isaac II, made contact with the Crusaders. Alexios offered to reunite the Byzantine church with Rome, pay the Crusaders 200,000 silver marks, join the crusade, and provide all the supplies they needed to reach Egypt.^[116]

Thumb — The partition of the empire following the Fourth Crusade, c. 1204

The crusaders arrived at Constantinople in the summer of 1203 and quickly attacked, starting a major fire that damaged large parts of the city, and briefly seized control. Alexios III fled from the capital, and Alexios Angelos was elevated to the throne as Alexios IV along with his blind father Isaac. Alexios IV and Isaac II were unable to keep their promises and were deposed by Alexios V. The crusaders again took the city on 13 April 1204, and Constantinople was subjected to pillage and massacre by the rank and file for three days. Many priceless icons, relics and other objects later turned up in Western Europe, a large number in Venice. According to chronicler Niketas Choniates, a prostitute was even set up on the patriarchal throne.^[117] When order had been restored, the crusaders and the Venetians proceeded to implement their agreement; Baldwin of Flanders was elected emperor of a new Latin Empire, and the Venetian Thomas Morosini was chosen as patriarch. The lands divided up among the leaders included most of the former Byzantine possessions.^[118] Although Venice was more interested in commerce than conquering territory, it took key areas of Constantinople, and the Doge took the title of "Lord of a Quarter and Half a Quarter of the Roman Empire".^[119]

After the sack of Constantinople in 1204 by Latin crusaders, two Byzantine successor states were established: the Empire of Nicaea and the Despotate of Epirus. A third, the Empire of Trebizond, was created after Alexios Komnenos, commanding the Georgian expedition in Chaldia^[120] a few weeks before the sack of Constantinople, found himself de facto emperor and established himself in Trebizond. Of the three successor states, Epirus and Nicaea stood the best chance of reclaiming Constantinople. The Nicaean Empire struggled to survive the next few decades, however, and by the mid-13th century it had lost much of southern Anatolia.^[121] The weakening of the Sultanate of Rûm following the Mongol invasion in 1242–1243 allowed many beyliks and ghazis to set up their own principalities in Anatolia, weakening the Byzantine hold on Asia Minor.^[122] Two centuries later, one of the Beys of these beyliks, Osman I, would establish the Ottoman Empire that would eventually conquer Constantinople.^[123] However, the Mongol invasion also gave Nicaea a temporary respite from Seljuk attacks, allowing it to concentrate on the Latin Empire to its north.

The Empire of Nicaea, founded by the Laskarid dynasty, managed to recapture Constantinople in 1261 and defeat Epirus. This led to a short-lived revival of Byzantine fortunes under Michael VIII Palaiologos, but the war-ravaged empire was ill-equipped to deal with the enemies that surrounded it. To maintain his campaigns against the Latins, Michael pulled troops from Asia Minor and levied crippling taxes on the peasantry, causing much resentment.^[124] Massive construction projects were completed in Constantinople to repair the damage of the Fourth Crusade, but none of these initiatives were of any comfort to the farmers in Asia Minor suffering raids from Muslim ghazis.^[125]

Rather than holding on to his possessions in Asia Minor, Michael chose to expand the empire, gaining only short-term success. To avoid another sacking of the capital by the Latins, he forced the Church to submit to Rome, again a temporary solution for which the peasantry hated Michael and Constantinople.^[125] The efforts of Andronikos II and later his grandson Andronikos III marked Byzantium's last genuine attempts to restoring the glory of the empire. However, the use of mercenaries by Andronikos II often backfired, with the Catalan Company ravaging the countryside and increasing resentment towards Constantinople.^[126]

Fall

The situation became worse for Byzantium during the civil wars after Andronikos III died. A six-year-long civil war devastated the empire, allowing the Serbian ruler Stefan Dušan to overrun most of the empire's remaining territory and establish a Serbian Empire. In 1354, an earthquake at Gallipoli devastated the fort, allowing the Ottomans (who were hired as mercenaries during the civil war by John VI Kantakouzenos) to establish themselves in Europe.^[127]^[128] By the time the Byzantine civil wars had ended, the Ottomans had defeated the Serbians and subjugated them as vassals. Following the Battle of Kosovo, much of the Balkans became dominated by the Ottomans.^[129]

Constantinople by this stage was underpopulated and dilapidated. The population of the city had collapsed so severely that it was now little more than a cluster of villages separated by fields. On 2 April 1453, Sultan Mehmed's army of 80,000 men and large numbers of irregulars laid siege to the city.^[130] Despite a desperate last-ditch defence of the city by the massively outnumbered Christian forces (c. 7,000 men, 2,000 of whom were foreign),^[131] Constantinople finally fell to the Ottomans after a two-month siege on 29 May 1453. The final Byzantine emperor, Constantine XI Palaiologos, was last seen casting off his imperial regalia and throwing himself into hand-to-hand combat after the walls of the city were taken.^[132]