Constantine V

Constantine V convened the Council of Hieria, which formally condemned the veneration of icons as idolatry. This council established iconoclasm as official Byzantine Church doctrine, intensifying the religious controversy that divided the empire.

Following the Council of Hieria, Constantine V intensified persecution of icon venerators. Monks were imprisoned, executed, or forced to marry. Monasteries were confiscated and converted to barracks or secular use. This policy deepened the iconoclast schism.

Constantine V led nine major campaigns against the Bulgarian Empire, achieving several victories including the Battle of Marcellae (759) and the Battle of Anchialus (763). These campaigns temporarily weakened Bulgaria but did not destroy it.

Constantine V oversaw the restoration of the Aqueduct of Valens, which had been damaged by the Avars. The repaired aqueduct restored water supply to Constantinople, improving urban infrastructure and public health.

Constantine V died while on campaign against the Bulgars. His death occurred during a military expedition, and he was succeeded by his son Leo IV. His campaigns had temporarily checked Bulgarian expansion but left the empire exhausted.