the Empire was threatened by their projects of conquest beyond the Adriatic, projects which aimed at Constantinople itself.
Four great attempts against the Empire were made by the Normans; they were unsuccessful, but they heralded the Western conquest of 1204. (1) Expedition of Robert Guiscard, 1081-85, repelled by Alexius with help of Venice; (2) Bohemond's expedition, 1105-7, foiled by the able strategy of Alexius; (3) the invasion of Greece by Roger of Sicily, 1147; Venice supported Manuel Comnenus, and the Normans were driven from Corfu, 1149; (4) the expedition of William II. of Sicily, 1185, who succeeded in capturing Thessalonica; the invaders were defeated at Demetritsa, but they gained the islands of Cephallenia and Zacynthus.
The two most important events in the reign of Alexius were the prices which he paid for help against his enemies. (1) He was obliged (1084) to grant to Venice (which had become independent of the Empire in the 9th century; see Venice), in return for her naval aid against the Normans, commercial privileges which practically made the Empire commercially dependent on the Republic. (2) He sought auxiliary forces in western Europe to help him against the Seljuks; the answer of the pope and Latin Christendom was the First Crusade—a succour very different from that which he desired. Through his tact and discretion, the state was safely steered through the dangers with which the disorderly hosts of barbarous allies menaced it, and the immediate results were salutary; large parts of Asia Minor, including Nicaea, were restored to the Empire, which was thus greatly strengthened in the East while the Turks were weakened (see Crusades). But for this help Byzantium might not have recovered the transient strength and brilliance which it displayed under Manuel. In Asia Minor the Crusaders kept the terms of their agreement to restore to the emperor what had belonged to him; but on capturing Antioch (1098) they permitted the Norman Bohemond to retain it, in flagrant violation of their oaths; for to Antioch if to any place the emperor had a right, as it had been his a few years before. This was in itself sufficient to cause a breach between Byzantium and the Latin kingdom of Jerusalem (founded 1099). But otherwise the new political situation created by the Crusade was dangerous, ultimately fatal, to the Empire. For its lands and seas became a highway from western Europe to the Latin colonies in Syria; the Byzantine government was forced to take precautions to protect itself against the crusading expeditions which travelled to the Holy Land; and these precautions were regarded by the western powers as a hindrance to the sacred objects of the crusades. The bitter religious antagonism between the Greek and Latin Christians increased the mutual distrust and the danger.
The history of the new relations between East and West dating from the First Crusade is closely connected with the history of the futile attempts at bringing about a reunion between the Greek and Latin Churches, which had severed communion in 1054 (see below). To heal the schism and bring the Greek Church under the domination of Rome was a principal object of papal policy from Gregory VII. forward. The popes alternated between two methods for attaining this, as circumstances dictated: namely, a peaceful agreement—the policy of union; or an armed occupation of the Empire by some western power (the Normans)—the policy of conquest. Their views varied according to the vicissitudes of their political situation and their struggles with the western emperors. The eastern emperors were also constantly preoccupied with the idea of reconciliation, constantly negotiating with a view to union; but they did not care about it for its own sake, but only for political advantages which it might bring, and their subjects were bitterly opposed to it. Manuel Comnenus during the first part of his reign was the close friend and ally of the western emperor Conrad III., but after Conrad's death, he formed the ambitious plan of realizing in Europe a sovereignty like that of Justinian, and hoped to compass it in conjunction with Rome, the enemy of the Hohenstaufen. His forward policy carried war into Italy; he seized Ancona. But his strength was unequal to such designs. His Latin sympathies, no less than his financial extravagance, made him highly unpopular at home; and the national lack of sympathy with his Western policy was exhibited—after the revolution which overthrew his son Alexius and raised his cousin Andronicus I. to the throne—by the awful massacre of the Latin residents at Constantinople in 1182, for which the expedition of William of Sicily (see above) and the massacre of the people of Thessalonica was the revenge. The short reign of the wicked and brilliant Andronicus was in all respects a reaction, prudent, economical and popular. His fall was due to the aristocracy against whom his policy was directed, and the reign of Isaac Angelus undid his efforts and completed the ruin of the state. Oppressive taxation caused a revolt of the Bulgarian and Walachian population in the European provinces; the work of Zimisces and Basil was undone, and a new Bulgarian kingdom was founded by John Asen—a decisive blow to the Greek predominance which the Macedonian emperors seemed to have established.
In the fatal year 1204 the perils with which the eastward expansion of western Christendom (the Crusades, and the commercial predominance and ambitions of Venice) had long menaced the Empire, culminated in its conquest and partition. It was due to a series of accidents that the cloud burst at this moment, but the conditions of such a catastrophe had long been present. Isaac Angelus was dethroned by his brother Alexius III., and his son escaped (1201) to the west, where arrangements were being made for a new crusade, which Venice undertook to transport to the Holy Land. The prince persuaded Philip of Swabia (who had married his sister) and Boniface of Montferrat to divert the expedition to Byzantium, in order to restore his father and himself to the throne, promising to furnish help to the Crusade and to reconcile the Greek Church with Rome; Venice agreed to the plan; but Pope Innocent III., the enemy of Philip, forbade it. Isaac and his son, Alexius IV., were restored without difficulty in 1203, and the crusading forces were prepared to proceed to Palestine, if Alexius had performed his promises. But the manner of this restoration, under Latin auspices, was intensely unpopular; he was not unwilling, but he was unable, to fulfil his pledges; and a few months later he was overthrown in favour of one who, if an upstart, was a patriot, Alexius V. Then the Crusaders, who were waiting encamped outside the city, resolved to carry out the design which the Normans had repeatedly attempted, and put an end to the Greek Empire. The leaders of the Fourth Crusade must be acquitted of having formed this plan deliberately before they started; it was not conceived before 1204. They first arranged how they would divide the Empire amongst themselves (March); then they captured the city, which had to endure the worst barbarities of war. In partitioning the Empire, which was now to become the spoil of the conquerors, the guiding mind was the Venetian leader, the blind doge, Henry Dandolo. He looked to the interests of Venice from the narrowest point of view, and in founding the new Latin Empire, which was to replace the Greek, it was his aim that it should be feeble, so as to present no obstacles to Venetian policy. The Latin Empire of Romania was a feudal state like the kingdom of Jerusalem; the emperor was suzerain of all the princes who established themselves on Greek territory; under his own immediate rule were Constantinople, southern Thrace, the Bithynian coast, and some islands in the Aegean. But he was hampered from the beginning by dependence on Venice, want of financial resources, and want of a fleet; the feudal princes, occupied with their separate interests, gave him little support in his conflict with Greeks and Bulgarians; at the end of ten years the worthless fabric began rapidly to decline, and the efforts of the popes, for whom it was the means of realizing Roman supremacy in the East, were unavailing to save it from the extinction to which it was doomed in its cradle.
The original Act of Partition (which gave ¼ of the Byzantine territory to the future emperor, ⅜ to Venice, the remaining ⅜ to the Crusaders) could hardly be carried out strictly, as the territory was still to be won. The most important vassal state was the kingdom of Thessalonica, including Thessaly, which was assigned to Boniface of Montferrat. But it was conquered by the Greeks of Epirus in 1222. The chief of the territories taken by Venice
