The World of the Ancient Romans - Warfare
Wars against the Muslims
By 867, the empire had re-stabilised its position in both the east and the west, and the efficiency of its defensive military structure enabled its emperors to begin planning wars of reconquest in the east.
The process of reconquest began with variable fortunes. The temporary reconquest of Crete (843) was followed by a crushing Byzantine defeat on the Bosporus, while the emperors were unable to prevent the ongoing Muslim conquest of Sicily (827–902). Using present day Tunisia as their launching pad, the Muslims conquered Palermo in 831, Messina in 842, Enna in 859, Syracuse in 878, Catania in 900 and the final Byzantine stronghold, the fortress of Taormina, in 902.
These drawbacks were later counterbalanced by a victorious expedition against Damietta in Egypt (856), the defeat of the Emir of Melitene (863), the confirmation of the imperial authority over Dalmatia (867), and Basil I's offensives towards the Euphrates (870s). Unlike the deteriorating situation in Sicily, Basil I handled the situation in southern Italy well enough and the province would remain in Byzantine hands for the next 200 years.
In 904, disaster struck the empire when its second city, Thessaloniki, was sacked by an Arab fleet led by the Byzantine renegade Leo of Tripoli. The Byzantine military responded by destroying an Arab fleet in 908, and sacking the city of Laodicea in Syria two years later. Despite this revenge, the Byzantines were still unable to strike a decisive blow against the Muslims, who inflicted a crushing defeat on the imperial forces when they attempted to regain Crete in 911.
The situation on the border with the Arab territories remained fluid, with the Byzantines alternatively on the offensive or defensive. The Varangians, who attacked Constantinople for the first time in 860, constituted another new challenge. In 941 they appeared on the Asian shore of the Bosporus, but this time they were crushed, showing the improvements in the Byzantine military position after 907, when only diplomacy had been able to push back the invaders. The vanquisher of the Varangians was the famous general John Kourkouas, who continued the offensive with other noteworthy victories in Mesopotamia (943): these culminated in the reconquest of Edessa (944), which was especially celebrated for the return to Constantinople of the venerated Mandylion.
The soldier-emperors Nikephoros II Phokas (reigned 963–969) and John I Tzimiskes (969–976) expanded the empire well into Syria, defeating the emirs of north-west Iraq and reconquering Crete and Cyprus. At one point under John, the empire's armies even threatened Jerusalem, far to the south. The emirate of Aleppo and its neighbours became vassals of the empire in the east, where the greatest threat to the empire was the Fatimid caliphate. After much campaigning, the last Arab threat to Byzantium was defeated when Basil II rapidly drew 40,000 mounted soldiers to relieve Roman Syria. With a surplus of resources and victories thanks to the Bulgar and Syrian campaigns, Basil II planned an expedition against Sicily to re-take it from the Arabs there. After his death in 1025, the expedition set off in the 1040s and was met with initial, but stunted success.
Relations with the Kievan Rus'
Between 850 and 1100 the Empire developed a mixed relationship with a new state that emerged to the north across the Black Sea, that of the Kievan Rus'. This relationship would have long-lasting repercussions in the history of East Slavs. Byzantium quickly became the main trading and cultural partner for Kiev, but relations were not always friendly. The most serious conflict between the two powers was the war of 968-971 in Bulgaria, but several Rus' raiding expeditions against the Byzantine cities of the Black Sea coast and Constantinople itself are also recorded. Although most were repulsed, they were concluded by trade treaties that were generally favourable to the Rus'.
Rus'-Byzantine relations became closer following the marriage of the porphyrogenita Anna to Vladimir the Great, and the subsequent Christianization of the Rus': Byzantine priests, architects and artists were invited to work on numerous cathedrals and churches around Rus', expanding Byzantine cultural influence even further. Numerous Rus' served in the Byzantine army as mercenaries, most notably as the famous Varangian Guard.
Crisis and fragmentation
Byzantium soon 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 (963-969), John Tzimiskes and Basil II changed the military divisions (τάγματα, tagmata) from a rapid response, primarily defensive, citizen army into a professional, campaigning army increasingly manned by mercenaries. Mercenaries, however, were expensive and as the threat of invasion receded in the 10th century, so did the need for maintaining large garrisons and expensive fortifications. Basil II left a burgeoning treasury upon his death, but neglected to plan for his succession. None of his immediate successors had any particular military or political talent and the administration of the Empire increasingly fell into the hands of the civil service. Efforts to revive the Byzantine economy only resulted in inflation and a debased gold coinage. The army was now seen as both an unnecessary expense and a political threat. Therefore, native troops were cashiered and replaced by foreign mercenaries on specific contract.
At the same time, the Empire was faced with new, ambitious enemies. Byzantine provinces in southern Italy faced the Normans, who arrived in Italy at the beginning of the 11th century. During a period of strife between Constantinople and Rome which ended in the East-West Schism of 1054, the Normans began to advance, slowly but steadily, into Byzantine Italy.
It was in Asia Minor, however, that the greatest disaster would take place. The Seljuq Turks made their first explorations across the Byzantine frontier into Armenia in 1065 and in 1067. 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 Manzikert Romanos not only suffered a surprise defeat at the hands of Sultan Alp Arslan, but was also captured. Alp Arslan treated him with respect, and imposed no harsh terms on the Byzantines. In Constantinople, however, a coup took place in favor of Michael Doukas, who soon faced the opposition of Nikephoros Bryennios and Nikephoros Botaneiates. By 1081 the Seljuks expanded their rule over virtually the entire Anatolian plateau from Armenia in the east to Bithynia in the west and founded their capital in Nicea.
Komnenian dynasty and the crusaders
In the context of Byzantine history, the period from about 1081 to about 1185 is often known as the Komnenian or Comnenian period, after the Komnenos dynasty. Together, the five Komnenian emperors (Alexios I, John II, Manuel I, Alexios II and Andronikos I) ruled for 104 years, presiding over a sustained, though ultimately incomplete, restoration of the military, territorial, economic and political position of the Byzantine Empire. As a human institution, Byzantium under the Komnenoi played a key role in the history of the Crusades in the Holy Land, while also exerting enormous cultural and political influence in Europe, the Near East, and the lands around the Mediterranean sea. The Komnenian emperors, particularly John and Manuel, exerted great influence over the Crusader states of Outremer, whilst Alexios I played a key role in the course of the First Crusade, which he helped bring about.
The Komnenoi also made a significant contribution to the history of Asia Minor. By reconquering much of the region, the Komnenoi set back the advance of the Turks in Anatolia by more than two centuries. In the process, they planted the foundations of the Byzantine successor states of Nicaea, Epirus and Trebizond. Meanwhile, their extensive programme of fortifications has left an enduring mark upon the Anatolian landscape, which can still be appreciated today.