The Fourth Crusade and the establishment of the Latin Empire
In 1195 Isaac II was deposed and blinded by his brother Alexius III. The Westerners, who had again blamed the failure of their crusade on the Byzantines, saw ways of exploiting the situation. The emperor Henry VI had united the Norman Kingdom of Sicily with the Holy Roman Empire. He inherited the ambitions of both to master Constantinople, and his brother, Philip of Swabia, was married to a daughter of the dethroned Isaac II. Alexius bought off the danger by paying tribute to Henry, but Henry died in 1197. The idea had now gained ground in the West that the conquest of Constantinople would solve a number of problems and would be of benefit not only to trade but also to the future of the crusade and the church. In 1198 Innocent III was elected pope. The new rulers of Hungary, Serbia, and Bulgaria all turned to him for the recognition of the sovereignty that Byzantium would not give them.

It was under Innocent's inspiration that the Fourth Crusade was launched, and it was by the diversion of that crusade from its purpose and objective that the conquest and colonization of the Byzantine Empire by the West was realized. A multiplicity of causes and coincidences led up to the event, but the ambition of Venice, which supplied the ships, must rank high among them. A plausible excuse was offered by the cause of restoring Isaac II, whose son Alexius IV had escaped to the West to seek help, and who made lavish promises of reward to his benefactors. But when, in 1203, the crusaders drove Alexius III out of Constantinople, Isaac II and his son proved incapable either of fulfilling the promises or of stifling the anti-Latin prejudice of their people, who proclaimed an emperor of their own in the person of Alexius V. The Venetians and crusaders therefore felt justified in taking their own reward by conquering and dividing Constantinople and the Byzantine provinces among themselves. The city fell to them in April 1204. They worked off their resentment against the inhabitants in an unparalleled orgy of looting and destruction, which did irreparable damage to the city and immeasurable harm to East-West understanding.

The Venetians, led by their doge, Enrico Dandolo, gained most from the enterprise by appropriating the principal harbors and islands on the trade routes. The crusaders set about the conquest of the European and Asiatic provinces. The first Latin emperor, Baldwin I, was the suzerain of the feudal principalities that they established in Thrace, Thessalonica, Athens, and the Morea (Peloponnese). He soon came into conflict with the ruler of Bulgaria. Still more serious was the opposition offered by the three provincial centres of Byzantine resistance. At Trebizond (Trabzon) on the Black Sea, two brothers of the Comnenian family laid claim to the imperial title. In Epirus in northwestern Greece Michael Angelus Ducas, a relative of Alexius III, made his capital at Arta and harassed the crusader states in Thessaly. The third centre of resistance was based on the city of Nicaea in Anatolia, where Theodore I Lascaris, another relative of Alexius III, was crowned as emperor in 1208 by a patriarch of his own making. Of the three, Nicaea lay nearest to Constantinople, between the Latin Empire and the Seljuq sultanate of Rum; and its emperors proved worthy of the Byzantine traditions of fighting on two fronts at once and of skillful diplomacy. Theodore Lascaris and his son-in-law John III Vatatzes built up at Nicaea a microcosm of the Byzantine Empire and church in exile. The Latins were thus never able to gain a permanent foothold in Anatolia; and even in Europe their position was constantly threatened by the Byzantine rulers of northern Greece, though in the centre and south of the country their conquests were more lasting.

The most successful of the Latin emperors was Baldwin's brother, Henry of Flanders, after whose death in 1216 the Latin Empire lost the initiative and the recovery of Constantinople became a foreseeable goal for the Byzantines in exile. The Latin regime was prolonged less by its own vitality than by the inability of the successor states of Epirus and Nicaea to cooperate. In 1224 Theodore Ducas of Epirus, who had extended his territories across the north of Greece and far into Bulgaria, wrested Thessalonica from the Latins and was crowned emperor there in defiance of the Emperor in Nicaea. In 1230, however, he was defeated in battle against the Bulgars before reaching Constantinople; and his defeat gave John III Ducas Vatatzes the chance to extend his own empire into Europe, to ally with the Bulgars, and so to encircle Constantinople. Theodore's successor was made to renounce his imperial title, and Thessalonica surrendered to the empire of Nicaea in 1246. The Mongol invasion of Anatolia, which had meanwhile thrown the East into confusion, was of great benefit to Nicaea, for it weakened the Seljuq sultanate and isolated the rival empire of Trebizond.

John Vatatzes might well have crowned his achievements by taking Constantinople had he not died in 1254. When his son Theodore II Lascaris (1254-58) died in 1258, leaving an infant son, John IV, the regency and then the throne in Nicaea were taken over by Michael VIII Palaeologus (reigned 1259-82). Michael came from one of the aristocratic families of Nicaea whom Theodore II had mistrusted. But it was he who carried the work of the Lascarid emperors to its logical conclusion. The Byzantine state in Epirus had revived under Michael II Ducas, who set his sights on Thessalonica. Despite several efforts to reach a diplomatic settlement, the issue between the rival contenders had finally to be resolved in battle at Pelagonia in Macedonia in 1259. Michael II was supported by William of Villehardouin, the French prince of the Morea, and by Manfred, the Hohenstaufen king of Sicily. The victory went to the army of Nicaea. Two years later a general of that army entered Constantinople. The last of the Latin emperors, Baldwin II, fled to Italy; and the Venetians were dispossessed of their lucrative commercial centre. In August 1261 Michael VIII was crowned as emperor in Constantinople; the boy heir to the throne of Nicaea, John IV Lascaris, was blinded and imprisoned. In this way, the dynasty of Palaeologus, the last to reign in Constantinople, was inaugurated.

The empire under the Palaeologi: 1261-1453
Byzantine Empire: The remnants of the Byzantine Empire in 1265.
The empire in exile at Nicaea had become a manageable and almost self-sufficient unit, with a thriving economy based on agriculture and, latterly, on trade with the Seljuqs. It had no navy but the land frontiers in Anatolia, policed by well-paid troops, were stronger than they had been since the 12th century. By stretching the frontiers into Europe the empire had not dissipated its strength; for the possession of Thessalonica balanced that of Nicaea. When the seat of government was moved from Nicaea to Constantinople, that balance was upset, the economy was re-oriented, and the defense system in Anatolia began to break down. Constantinople was still the New Jerusalem for the Byzantines. To leave it in foreign hands was unthinkable. But after the dismemberment of the empire by the Fourth Crusade, the city was no longer the focal point of an integrated structure. It was more like an immense city-state in the midst of a number of more or less independent provinces. Much of Greece and the islands remained in French or Italian hands. The Byzantine rulers of Epirus and Thessaly, like the emperors in Trebizond, refused to recognize Michael VIII as emperor. His treatment of the Lascarid heir of Nicaea, for which the patriarch Arsenius excommunicated him, appalled many of his own subjects and provoked what was known as the Arsenite schism in the Byzantine Church. Many in Anatolia, loyal to the memory of the Lascarid emperors who had enriched and protected them, condemned Michael VIII as a usurper.

Michael VIII
The new dynasty was thus founded in an atmosphere of dissension, but its founder was determined that it should succeed. He took measures for the rehabilitation, repopulation, and defense of Constantinople. He stimulated a revival of trade by granting privileges to Italian merchants. The Genoese, who had agreed to lend him ships for the recovery of the city from their Venetian rivals, were especially favoured; and soon they had built their own commercial colony at Galata opposite Constantinople, and cornered most of what had long been a Venetian monopoly. Inevitably, this led to a conflict between Genoa and Venice, of which the Byzantines were the main victims. Some territory was taken back from the Latins, notably in the Morea and the Greek islands. But little was added to the imperial revenue; and Michael VIII's campaigns there and against Epirus and Thessaly ate up the resources that had been accumulated by the emperors at Nicaea.

The dominating influence on Byzantine policy for most of Michael's reign was the threat of reconquest by the Western powers. Charles of Anjou, the brother of the French king Louis IX, displaced Manfred of Sicily and inherited his title in 1266; he then organized a coalition of all parties interested in re-establishing the Latin empire, posing as the pope's champion to lead a crusade against the schismatic Greeks. Michael VIII countered this threat by offering to submit the Church of Constantinople to the see of Rome, thereby inviting the pope's protection and removing the only moral pretext for a repetition of the Fourth Crusade. The offer to reunite the churches had been made as a diplomatic ploy to previous popes by previous emperors, but never in such compelling circumstances. Pope Gregory X accepted it at its face value, and at the second Council of Lyon in 1274 a Byzantine delegation professed obedience to the Holy See in the name of their emperor. Michael's policy, sincere or not, was violently opposed by most of his people, and he had to persecute and imprison large numbers of them in order to persuade the papacy that the union of the churches was being implemented. Later popes were not convinced by the pretense. In 1281 Charles I (Charles of Anjou) invaded the empire. His army was beaten back in Albania, but he at once prepared a new invasion by sea, supported by Venice, Serbia, Bulgaria, and the separatist rulers of northern Greece. His plans, however, were wrecked in 1282 by a rebellion in Sicily called the Sicilian Vespers and by the intervention of Peter III of Aragon, which the Byzantines encouraged. Michael VIII died at the end of the same year. He had saved his empire from its most persistent enemy, but he died condemned by his church and people as a heretic and a traitor.

Whatever sins he may have committed in the eyes of the Orthodox Church, it is true that Michael VIII, by concentrating on the danger from the West, neglected, if he did not betray, the eastern provinces where he had come to power. Frontier defense troops in Anatolia were withdrawn to Europe or neglected, and bands of Turkish raiders, driven westward by the upheaval of the Mongol invasion, began to penetrate into Byzantine territory. Like the Seljuqs in the 11th century, the new arrivals found little organized opposition. Some of the local Byzantines even collaborated with them out of their own antipathy to the Emperor in Constantinople. By about 1280 the Turks were plundering the fertile valleys of western Anatolia, cutting communications between the Greek cities, and their emirs were beginning to carve out small principalities. Michael VIII's network of diplomacy covered the Mongols of Iran and the Golden Horde in Russia, as well as the Mamluks of Egypt. But diplomacy was ineffective against Muslim Ghazis (warriors inspired by the ideal of holy war); by the time the threat from Italy was removed in 1282, it was almost too late to save Byzantine Anatolia.

Nor was it possible to raise armies to fight in Europe and Asia simultaneously. The native recruitment fostered by the Comnenian emperors had fallen off since 1261. Estates held in pronoia had become hereditary possessions of their landlords, who ignored or were relieved of the obligation to render military service to the government. The knights of the Fourth Crusade had found many familiar elements of feudalism in the social structure of the Byzantine provinces. By the end of the 13th century the development had gone much further. The officers of the Byzantine army were still mostly drawn from the native aristocracy. But the troops were hired, and the cost of maintaining a large army in Europe, added to the lavish subsidies that Michael VIII paid to his friends and allies, crippled the economy.

Andronicus II
Michael's son Andronicus II (reigned 1282-1328) unwisely attempted to economize by cutting down the size of the army and disbanding the navy. Unemployed Byzantine sailors sold their services to the new Turkish emirs, who were already raiding the Aegean islands. The Genoese became the suppliers and defenders of Constantinople by sea, which excited the jealousy of the Venetians to the pitch of war and led to the first of a series of naval battles off Constantinople in 1296. In reaction against his father's policy, Andronicus II pursued a line of almost total isolation from the papacy and the West. The union of Lyon was solemnly repudiated and Orthodoxy restored, to the deep satisfaction of most Byzantines. But there were still divisive conflicts in society. The Arsenite schism in the church was not healed until 1310; the rulers of Epirus and Thessaly remained defiant and kept contact with the successors of Charles I in Italy; and the people of Anatolia aired their grievances in rebellion. As the Turks encroached on their land, refugees in growing numbers fled to the coast or to Constantinople, bringing new problems for the government. In 1302 a band of Turkish warriors defeated the Byzantine army near Nicomedia in northwestern Anatolia. Its leader, Osman I, was the founder of the Osmanli, or Ottoman, people, who were soon to overrun the Byzantine Empire in Europe.

In 1303 Andronicus hired a professional army of mercenaries, the Grand Catalan Company. The Catalans made one successful counterattack against the Turks in Anatolia. But they were unruly and unpopular, and when their leader was murdered they turned against their employers. For some years they used the Gallipoli Peninsula as a base from which to ravage Thrace, inviting thousands of Turks to come over and help them. The Catalans finally moved west; in 1311 they conquered Athens from the French and established the Catalan Duchy of Athens and Thebes. The Turks whom they left behind were not ejected from Gallipoli until 1312. The cost of hiring the Catalans, and then of repairing the damage that they had done, had to be met by desperate measures. The face value of the Byzantine gold coin, the hyperpyron, was lowered when its gold content was reduced to a mere 50 percent; and the people had to bear still greater burdens of taxation--some payable in kind by farmers. Inflation and rising prices led to near famine in Constantinople, the population of which was swollen by vast numbers of refugees.


Cultural revival
Materially, the empire seemed almost beyond hope of recovery in the early 14th century, but spiritually and culturally it showed a remarkable vitality. The church, no longer troubled over the question of union with Rome, grew in prestige and authority. The patriarchs of Constantinople commanded the respect of all the Orthodox churches, even beyond the imperial boundaries; and Andronicus II, himself a pious theologian, yielded to the patriarch the ancient right of imperial jurisdiction over the monastic settlement on Mt. Athos. There was a new flowering of the Byzantine mystical tradition in a movement known as Hesychasm, whose chief spokesman was Gregory Palamas, a monk from Athos. The theology of the Hesychasts was thought to be heterodox by some theologians, and a controversy arose in the second quarter of the 14th century that had political undertones and was as disruptive to the church and state as the Iconoclastic dispute had been in an earlier age. It was not resolved until 1351.

The revival of mystical speculation and the monastic life may have been in part a reaction against the contemporary revival of secular literature and learning. Scholarship of all kinds was patronized by Andronicus II. As in the 11th century, interest was mainly centred on a rediscovery of ancient Greek learning. The scholar Maximus Planudes compiled a famous anthology and translated a number of Latin works into Greek, though knowledge of Latin was rare and most of the Byzantine scholars prided themselves on having in their Hellenic heritage an exclusive possession that set them apart from the Latins. A notable exception was Demetrius Cydones who, like Michael Psellus, managed affairs of state for a number of emperors for close to 50 years. Cydones translated the works of Thomas Aquinas into Greek; he was the forerunner of a minority of Byzantine intellectuals who joined the Roman Church and looked to the West to save their empire from ruin. More typical of his class was Theodore Metochites, the Grand Logothete, or chancellor, of Andronicus II, whose encyclopaedic learning rivaled that of Psellus. His pupil Nicephorus Gregoras, in addition to his researches in philosophy, theology, mathematics, and astronomy, wrote a history of his age. The tradition of Byzantine historiography, maintained by George Acropolites, the historian of the Empire of Nicaea, was continued in the 14th century by George Pachymeres, by Gregoras, and finally by the emperor John VI Cantacuzenus, who wrote his memoirs after his abdication in 1354.

Andronicus III and John Cantacuzenus
The histories they wrote tell more of politics and personalities than of the underlying social and economic tensions in their society that were to find expression in a series of civil wars. Trouble broke out in 1320 when Andronicus II, purely for family reasons, disinherited his grandson Andronicus III. The cause of the young emperor was taken up by his friends, and there was periodic warfare from 1321 to 1328, when the older Andronicus had to yield the throne. It was in some ways a victory for the younger generation of the aristocracy, of whom the leading light was John Cantacuzenus. It was he who guided the empire's policies during the reign of Andronicus III (1328-41). They were men of greater drive and determination, but the years of fighting had made recovery still more difficult and had given new chances to their enemies. In 1329 they fought and lost a battle at Pelekanon (near Nicomedia) against Osman's son, Orhan, whose Turkish warriors went on to capture Nicaea in 1331 and Nicomedia in 1337. Northwestern Anatolia, once the heart of the empire, was now lost. There seemed no alternative but to accept the fact and to come to terms with the Ottomans and the other Turkish emirs. By so doing, Andronicus III and Cantacuzenus were able to call on the services of almost limitless numbers of Turkish soldiers to fight for them against their other enemies: the Italians in the Aegean islands and the Serbs and the Bulgars in Macedonia and Thrace.

The power of Serbia, which Andronicus II had managed to control by diplomatic means, grew alarmingly after the accession of Stefan Dusan to the Serbian throne in 1331. Dusan exploited to the full the numerous embarrassments of the Byzantines and in 1346 announced his ambitions by having himself crowned as emperor of the Serbs and Greeks. The greatest practical achievement of Andronicus III was the restoration to Byzantine rule of the long-separated provinces of Epirus and Thessaly. But only a few years later, in 1348, the whole of northern Greece was swallowed up in the Serbian Empire of Stefan Dusan.

When Andronicus III died in 1341, civil war broke out for a second time. The contestants on that occasion were John Cantacuzenus, who had expected to act as regent for the boy-heir John V, and his political rivals led by his former partisan Alexius Apocaucus, the patriarch John Calecas, and the empress mother Anne of Savoy, who held power in Constantinople. Cantacuzenus, befriended and then rejected by Dusan of Serbia, was crowned as Emperor John VI in Thrace in 1346; and, with the help of Turkish troops, he fought his way to victory in the following year. Like Romanus Lecapenus, he protested that he was no more than the protector of the legitimate heir to the throne, John V Palaeologus. His brief reign, from 1347 to 1354, might have turned the tide of Byzantine misfortunes had not the second civil war provoked unprecedented social and political consequences. In the cities of Thrace and Macedonia the people vented their dissatisfaction with the ruling aristocracy by revolution. It was directed mainly against Cantacuzenus and the class that he represented. The movement was most memorable and lasting in Thessalonica, where a faction known as the Zealots seized power in a coup d'état and governed the city as an almost independent commune until 1350.

The second civil war was consequently even more destructive of property and ruinous to the economy than the first. At the same time, in 1347, the Black Death decimated the population of Constantinople and other parts of the empire. John VI Cantacuzenus, nevertheless, did what he could to restore the economy and stability of the empire. To coordinate the scattered fragments of its territory he assigned them as appanages to individual members of the imperial family. His son Manuel took over the province of the Morea in 1349 with the rank of despot and governed it with growing success until his death in 1380; his eldest son, Matthew, was given a principality in Thrace; while the junior emperor John V, who had married a daughter of Cantacuzenus, ruled in Thessalonica after 1351.

Cantacuzenus also tried but failed to weaken the economic stranglehold of the Genoese by rebuilding a Byzantine war fleet and merchant navy. The effort involved him in warfare, first on his own and then as an unwilling partner of the Venetians against the Genoese, from which Byzantium emerged as the loser. The revenue of the Genoese colony at Galata, derived from custom dues, was now far greater than that of Constantinople. The empire's poverty was reflected in dilapidated buildings and falling standards of luxury. The crown jewels had been pawned to Venice during the civil war, and the Byzantine gold coin, hopelessly devalued, had given place in international trade to the Venetian ducat. More and more, Byzantium was at the mercy of its foreign competitors and enemies, who promoted and exploited the political and family rivalries among the ruling class. John Cantacuzenus was never popular as an emperor, and feeling against him came to a head when some of his Ottoman mercenaries took the occasion of the destruction of Gallipoli by earthquake to occupy and fortify the city in March 1354. It was their first permanent establishment in Europe, at the key point of the crossing from Asia. In November of the same year John V Palaeologus, encouraged by the Anti-Cantacuzenist Party, forced his way into Constantinople. In December Cantacuzenus abdicated and became a monk. Though his son Matthew, who had by then been crowned as coemperor, fought on for a few years, the dynasty of Cantacuzenus was not perpetuated.

Turkish expansion
Byzantine Empire: The Byzantine Empire in 1355.

John Cantacuzenus' relationship with the Turks had been based on personal friendship with their leaders, among them Orhan, to whom he gave his daughter in marriage. But once the Turks had set up a base on European soil and had seen the possibilities of further conquest, such relationships were no longer practicable. Stefan Dusan, who very nearly realized his ambition to found a new Serbo-Byzantine empire, was the only man who might have prevented the subsequent rapid expansion of the Turks into the Balkans, but he died in 1355 and his empire split up. The new emperor, John V, hoped that the Western world would sense the danger, and in 1355 he addressed an appeal for help to the Pope. The popes were concerned for the fate of the Christian East but guarded in their offers to Constantinople so long as the Byzantine Church remained in schism from Rome. In 1366 John V visited Hungary to beg for help, but in vain. In the same year his cousin Amadeo, count of Savoy, brought a small force to Constantinople and recaptured Gallipoli from the Turks, who had by then advanced far into Thrace. Amadeo persuaded the Emperor to go to Rome and make his personal submission to the Holy See in 1369. On his way home, John was detained at Venice as an insolvent debtor; during his absence the Turks scored their first victory over the successors of Stefan Dusan on the Marica River near Adrianople in 1371. The whole of Macedonia was open to them. The remaining Serbian princes and the ruler of Bulgaria became their vassals, and in 1373 the Emperor was forced to do the same.

Byzantium became a vassal state of the Turks, pledged to pay tribute and to provide military assistance to the Ottoman sultan. The possession of Constantinople thereafter was disputed by the Emperor's sons and grandsons in a series of revolutions, which were encouraged and sometimes instigated by the Turks, the Genoese, or the Venetians. John V's son Andronicus IV, aided by the Genoese and the sultan Murad I, mastered the city for three years (1376-79). He rewarded the Turks by giving back Gallipoli to them, and Murad made his first European capital at Adrianople. The Venetians helped John V to regain his throne in 1379, and the empire was once again divided into appanages under his sons. Only his second son, Manuel, showed any independence of action. For nearly five years, from 1382 to 1387, Manuel reigned as emperor at Thessalonica and laboured to make it a rallying point for resistance against the encroaching Turks. But the city fell to Murad's army in April 1387. When the Turks then drove deeper into Macedonia, the Serbs again organized a counteroffensive but were overwhelmed at Kossovo in 1389.

Manuel II and respite from the Turks
The loss of Thessalonica and the Battle of Kossovo sealed off Constantinople by land. The new sultan Bayezid I (1389-1402) intended to make it his capital; when Manuel II came to that throne at his father's death in 1391, the Sultan warned him that he was emperor only inside the city walls. The Turks already controlled the rest of Byzantine Europe, except for the south of Greece.

In 1393 Bayezid completed his conquest of Bulgaria, and soon afterward he laid siege to Constantinople. The blockade was to last for many years. Manuel II, like his father, pinned his hopes of rescue on the West. A great crusade against the Turks was organized by the King of Hungary, but it was defeated at Nicopolis on the Danube in 1396. In 1399 the French marshal Boucicaut, who had been at Nicopolis and had returned to the relief of Constantinople with a small army, persuaded Manuel to travel to western Europe to put the Byzantine case in person. From the end of 1399 to June 1403 the Emperor visited in Italy, France, and England, leaving his nephew John VII in charge of Constantinople. Manuel's journey did something to stimulate Western interest in Greek learning. His friend and ambassador in the West, Manuel Chrysoloras, a pupil of Demetrius Cydones, was appointed to teach Greek at Florence. The Pope instituted a defense fund for Constantinople. Interest and sympathy were forthcoming but little in the way of practical help. During Manuel's absence, however, the Ottomans were defeated at Ankara by the Mongol leader Timur (Tamerlane) in July 1402. Bayezid was captured and his empire in Asia was shattered. His four sons contended with each other to secure possession of the European provinces, which had been little affected by the Mongol invasion, and to reunite the Ottoman dominions. In these wholly unexpected circumstances the Byzantines found themselves the favoured allies first of one Turkish contender, then of another. The blockade of Constantinople was lifted. Thessalonica--with Mt. Athos and other places--was restored to Byzantine rule, and the payment of tribute to the sultan was annulled. In 1413 Mehmed I, helped and promoted by the emperor Manuel, triumphed over his rivals and became sultan of the reintegrated Ottoman Empire.

During his reign, from 1413 to 1421, the Byzantines enjoyed their last respite. Manuel II, aware that it could not last, made the most of it by strengthening the defenses and administration of the fragments of his empire. The most flourishing province in the last years was the Despotate of Morea. Its prosperity had been built up first by the sons of John Cantacuzenus (who died there in 1383) and then by the son and grandson of John V--Theodore I and Theodore II Palaeologus. Its capital city of Mistra became a haven for Byzantine scholars and artists and a centre of the last revival of Byzantine culture, packed with churches, monasteries, and palaces. Among its scholars was George Gemistus Plethon, a Platonist who dreamed of a rebirth of Hellenism on Hellenic soil.

Final Turkish assault
When Murad II became sultan, in 1421, the days of Constantinople and of Hellenism were numbered. In 1422 Murad revoked all the privileges accorded to the Byzantines by his father and laid siege to Constantinople. His armies invaded Greece and blockaded Thessalonica. The city was then a possession of Manuel II's son Andronicus, who in 1423 handed it over to the Venetians. For seven years Thessalonica was a Venetian colony, until, in March 1430, the Sultan assaulted and captured it. Meanwhile, Manuel II had died in 1425, leaving his son John VIII as emperor. John, who had already traveled to Venice and Hungary in search of help, was prepared to reopen negotiations for the union of the churches as a means of stirring the conscience of Western Christendom. His father had been skeptical about the benefits of such a policy, knowing that it would antagonize most of his own people and arouse the suspicion of the Turks. The proposal was made, however, at the Council of Florence in 1439, attended by the emperor John VIII, his patriarch, and many Orthodox bishops and dignitaries. After protracted and difficult discussions, they agreed to submit to the authority of Rome. The union of Florence was badly received by the citizens of Constantinople and by most of the Orthodox world. But it had its notable adherents, such as the bishops Bessarion of Nicaea and Isidore of Kiev, both of whom retired to Italy as cardinals of the Roman Church. Bessarion's learning and library helped to encourage further Western interest in Greek scholarship. The union of Florence also helped to stimulate a crusade against the Turks. Once again it was led by the king of Hungary, Wladyslaw III of Poland, supported by George Brankovic of Serbia and by János Hunyadi of Transylvania. But there were disagreements among its leaders, and the Christian army was annihilated at Varna in 1444.

The Byzantine collapse and the Ottoman triumph followed swiftly thereafter. In 1448 Constantine XI (or XII), the last emperor, left Mistra for Constantinople when his brother John VIII died without issue. His two other brothers, Thomas and Demetrius, continued to govern the Morea, the last surviving Byzantine province. In 1449 Mehmed II (sultan 1444-46 and 1451-81) began to prepare for the final assault on Constantinople. No further substantial help came from the West, and the formal celebration of the union of the churches in Hagia Sophia in 1452 was greeted with a storm of protest. Even in their extremity, the Byzantines would not buy their freedom at the expense of their Orthodox faith. They found the prospect of being ruled by the Turks less odious than that of being indebted to the Latins. When the crisis came, however, the Venetians in Constantinople, and a Genoese contingent commanded by Giovanni Giustiniani, wholeheartedly cooperated in the defense of the city. Mehmed II laid siege to the walls in April 1453. His ships were obstructed by a chain that the Byzantines had thrown across the mouth of the Golden Horn. The ships were therefore dragged overland to the harbor from the seaward side, bypassing the defenses. The Sultan's heavy artillery continually bombarded the land walls until, on May 29, some of his soldiers forced their way in. Giustiniani was mortally wounded. The emperor Constantine was last seen fighting on foot at one of the gates.

The Sultan allowed his victorious troops three days and nights of plunder before he took possession of his new capital. The Ottoman Empire had now superseded the Byzantine Empire; and some Greeks, like the contemporary historian Critobulus of Imbros, recognized the logic of the change by bestowing on the Sultan all the attributes of the emperor. The material structure of the empire, which had long been crumbling, was now under the management of the sultan-basileus. But the Orthodox faith was less susceptible to change. The Sultan acknowledged the fact that the church had proved to be the most enduring element in the Byzantine world, and he gave the Patriarch of Constantinople an unprecedented measure of temporal authority by making him answerable for all Christians living under Ottoman rule.

The last scattered pockets of Byzantine resistance were eliminated within a decade after 1453. Athens fell to the Turks in 1456-58, and in 1460 the two despots of Morea surrendered. Thomas fled to Italy, Demetrius to the Sultan's court. In 1461 Trebizond, capital of the last remnant of Greek empire, which had maintained its precarious independence by paying court to Turks and Mongols alike, finally succumbed; the transformation of the Byzantine world into the Ottoman world was at last complete

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