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Emperor Basil II the Bulgar Slayer (976–1025).
The eighth and ninth centuries were also dominated by controversy and religious division over Iconoclasm. Icons were banned by Leo and Constantine, leading to revolts by iconodules (supporters of icons) throughout the empire. After the efforts of Empress Irene, the Second Council of Nicaea met in 787, and affirmed that icons could be venerated but not worshipped. Irene is said to have endeavored to negotiate a marriage between herself and Charlemagne, but, according to Theophanes the Confessor, the scheme was frustrated by Aetios, one of her favourites. In 813, Leo V the Armenian restored the policy of iconoclasm, but in 843 Empress Theodora restored the veneration of the icons with the help of Patriarch Methodios. Iconoclasm played its part in the further alienation of East from West, which worsened during the so-called Photian Schism, when Pope Nicholas I challenged Photios' elevation to the patriarchate.
Macedonian dynasty and resurgence
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