History of the Byzantine Empire in the first half of the 9th century was marked by an inner crisis. Empress Irene was overthrown in 802 and replaced by the minister of finance Nikephoros I Logothetes (802-811) who was primarily concentrated on financial and military reorganization. The Byzantine Empire was at the time threatened by the rising power of the Bulgarians and the initial Byzantine success against the Bulgarian Khan Krum was followed by a disastrous defeat in the Battle of Pliska in 811. Nikephoros was killed in the battle and was succeeded by his son Staurakios who was overthrown in 812.
Staurakios was succeeded by his brother-in-law Michael I Rangabe (811-813) who recognized Charlemagne as basileus (emperor) probably due to the Bulgarian threat. Michael I Rangabe decided to deal with the Bulgarians but his army was severely defeated at Versinikia near Adrianople in 813. Michael I was deposed and replaced by Armenian general Leo V (813-820). Like his predecessor, Leo V had to deal with the Bulgarian threat but he reached a peace agreement with Krum’s successor Omurtag in 814. Leo V afterwards concentrated on inner politics and renewed Iconoclasm in 815 but he had less support than his iconoclastic predecessors in the 8th century. He was assassinated and replaced by Michael II the Amorian (820-829) in 820.
The reign of Michael II the Amorian was marked by the rebellion of Thomas the Slav in Asia Minor in 821 which resulted in the outbreak of a civil war. Michael II the Amorian managed to repulse Thomas’ siege of Constantinople but the civil war that lasted until 823 greatly weakened the Byzantine Empire which could not prevent the Arab conquest of Crete. The Arab threat continued during the reign of Michael’s son and successor Theophilos (829-842) whose reign was characterized by restitution of Iconoclasm. The movement against the worship of images finally ended after his death in 842.
Theophilos was succeeded by his son Michael III (842-867). His mother Empress Theodora acted as his regent during his minority but the government was eventually assumed by the secretary of state (logothete) Theoktistos Vriennion. Michael III overthrew the regency in 856 but his reign was strongly influenced by his uncle Bardas. The latter played a major role in the rebirth of Byzantine culture and political power, and supported the missions of Saint Cyril and Methodius to the Slavs. Bardas was assassinated by Michael’s favorite Basil of Macedonia in 866. Michael III made Basil a co-emperor but the latter ordered Michael’s assassination in 867, assumed the Byzantine throne as Basil I (867-886) and founded the Macedonian dynasty.
The Byzantine Empire consolidated its power during the Basil’s reign. He launched several military campaigns which resulted in the recapture of Southern Italy and strengthened the Byzantine eastern frontier. Basil I died on a hunting accident in 886 and was succeeded by his son Leo VI the Wise (886-912). He completed and issued the Basiica, a Greek translation and update of the law code of Justinian I which centralized the government and strengthened the imperial authority in the first year of his reign. Leo VI was not as successful as his father in foreign politics. He provoked a war with Simeon I of Bulgaria which resulted in the Byzantine defeat in the Battle of Bulgarophygon in 896, while his war against Bulgaria enabled the Arabs to invade the Byzantine territory and to capture Sicily in 902 and Thessaloniki in 907. Constantinople was attacked by the Kievan Rus but Leo VI managed to repulse the Kievan threat through negotiations and favorable political-commercial treaty.
The Byzantine Empire fell into an inner crisis which caused by the conflicts over the throne after Leo’s death in 912. The Byzantine throne was assumed by Leo’s brother Alexander (912-913) who renewed the conflict with Simeon I of Bulgaria by refusing to pay tribute. He died only after one year after accession to the Byzantine throne and was succeeded by a minor son of Leo VI, Constantine VII (913-920 and 945-959) and Patriarch Nicholas Mystikos as his regent. Advance of the Bulgarian forces forced the Patriarch to recognize Simeon I as Bulgarian Emperor and to accept marriage between Constantine VII and one of Simeon’s daughters. However, Nicholas was driven out of regency and Empress Zoe revoked all Nicholas’ concessions to Simeon I. The latter invaded Thrace and marched towards Corinth in 918. At the same time came to power admiral Romanos Lekapenos who arranged the marriage between Constantine VII and his daughter Helena in 919. He bacame basileopator (emperor-father) but crowned himself co-emperor one year later. The Bulgarians failed to capture Constantinople in 920, while the Bulgarian threat finally ceased after Simeon’s death in 927. The Byzantines afterwards concentrated on campaigns against the Arabs and extended the Byzantine borders far to the east.
Romanos’ sons Stephen and Constantine who feared that he will be succeeded by Constantine VII overthrew their father in 944. However, Constantine VII removed his brothers-in-law in 945 and reigned as sole emperor until his death in 959. He was succeeded by his son Romanos II (959-963) whose short reign is notable for his successful military campaigns. General Nikephoros Phokas captured Crete in 961, decisively defeated the Arabs at Saif ed-Daula and conquered Aleppo one year later. Romanos II died suddenly in 963 and the imperial title was won by general Nikephoros Phokas through marriage with Romanos’ widow Theophanu. However, Theophanu conspired against him and Nikephoros was assassinated by John Tzimiskes who assumed the Byzantine throne as John I (969-976).
John I settled the conflicts with Holy Roman Emperor Otto I over the possessions in Southern Italy and married his niece Theophanu with Otto I’s son Otto II in 972. John’s sudden death in 976 was followed by a civil war over his succession which was won by the eldest son of Romanos II, Basil II (979-1025) in 979. The Byzantine Empire under Basil II reached its height. Basil II decisively defeated the Bulgarians and annexed their territory in 1018. He was also successful in Southern Italy and Armenia but his reign is probably best known for increased Byzantine cultural influence in Kievan Rus, the Balkans and Capadocia.
The Byzantine Empire began to decline after Basil’s death in 1025. His successors Constantine VIII (1025-1028), Romanos III (1028-1034) and Michael IV (1034-1042) failed to limit the rising power of aristocracy and to prevent decentralization and weakening of state finances. Constantine IX (1042-1055) who tried to secure his position by favoring the nobility was faced with the Pecheneg invasion on the north and increased Norman pressure in Southern Italy, while the Seljuks Turks invaded Syria after the conquest of Baghdad in 1055. In addition, the differences between the Greek and Roman Churches resulted in the Great Schism and their final separation in 1054. The Macedonian dynasty became extinct after the death of Empress Theodora (1055-1056) and was followed by severe conflicts over the Byzantine throne.
Michael IV (1056-1057) who was chosen by Empress Theodora as her successor was forced to step down by Isaac I Komnenos (1057-1059). However, Isaac I soon came into conflict with the court bureaucracy as well as with the clergy and was forced to abdicate in 1059. He was succeeded by Constantine X Doukas (1059-1067) whose reign was characterized by further decline of the Byzantine Empire which suffered severe territorial losses under his son and successor Michael IV Doukas (1071-1078). The Normans under Robert Guiscard advanced in Sicily and Southern Italy, the Hungarians captured Belgrade in 1064, the Pechenegs penetrated into Greece, while Minor Asia was permanently lost after severe defeat of the Byzantine forces by the Seljuk Turks in the Battle of Manzikert in 1071. Foreign difficulties caused dissatisfaction with Michael’s reign and he was forced to abdicate in 1078. The Byzantine throne was assumed by Nikephoros III (1078-1081) but he was deposed in 1081.
Nikephoros III was succeeded by Alexios I Comnenus (Komnenos) (1081-1118) who founded the Komnenid Dynasty. The reign of Alexios I was marked by the First Crusade which was launched on his appeal to Pope Urban II. He managed to recover some of territory in Asia Minor, defeated Bohemund I of Antioch in the Battle of Dyrrhachium in 1107 and repulsed the Norman threat. However, he was faced with a serious rival in the Balkan Peninsula after the establishment of personal union between Hungary and Croatia. His successor John II Comnenus (1118-1143) managed to withstand all the attacks on the Byzantine Empire, defeated the Pechenegs who invaded Thrace and repulsed the Hungarians. He conquered the Principality of Antioch in 1137, transformed it into a vassal state and concluded a defensive alliance with the Holy Roman Empire against the Normans. However, his successor Manuel I Comnenus (1143-1180) was not able to pursue his father’s policy. Manuel I came into conflict with the Pope and Louis VII of France after the Second Crusade (1147-1149) and failed to reach an agreement with Holy Roman Emperor, Frederick I Barbarossa against Roger II of Sicily. He invaded Southern Italy in 1155 but he was forced to withdraw and cede Southern Italy to William I of Sicily after defeat at Brindisi in 1156. Manuel I achieved success in the Balkans by capturing Dalmatia, Croatia and Bosnia in 1167 and by extending his influence over Hungary and Serbia. However, his successful politics in the Balkans brought him into conflict with Venice which concluded an anti-Byzantine alliance with the Normans. Manuel I allied himself with Genoa (1169) and Pisa (1170) but Venice established itself as a leading sea power in the Mediterranean. He launched a military campaign against the Seljuk Turks in 1176 but the Byzantine forces were severely defeated at Myriocephalon.
Manuel I died in 1180 and was succeeded by Alexios II Comnenus (1180-1183) with his mother Maria of Antioch as his regent. However, Alexios II was forced to recognize Andronikos Comenus (1183-1185) as emperor shortly after his accession to the Byzantine throne. Andronikos’ brutal suppression of his opponents resulted in several revolts and the chaotic situation in the Byzantine Empire was taken advantage by William II of Sicily who invaded the Byzantine territory. Andrikos was deposed by Isaac II Angelos (1185-1195 and 1203-1204) during his absence from Constantinople. The new Byzantine Emperor repulsed the invaders but he was not able to prevent the further disintegration and decline of the Byzantine Empire which also marked the reign of his successor Alexios III Angelos (1195-1203). The Byzantine Empire under Alexios III Angelos lost its political influence in the Balkan Peninsula and Cyprus, while the Fourth Crusade resulted in the partition of the Byzantine Empire in 1204.