As part of the Eastern Roman Empire, Crete was left to the Byzantine Empire, of which it became an administrative region, with Gortyn as its capital. In early Byzantine times (4th - 6th centuries), the island lived in prosperity and peace, but from the late 6th century onwards the earlier urban centres fell into decline and the population moved into the countryside. The Arabs had control of the trade routes to the East, and external trade began to wane.
From the 7th century onwards the island was subject to repeated pirate raids, led mainly by the Arabs, which brought about the decline of coastal settlements. The inhabitants moved inland to small farming settlements. To deal with this new threat Crete was upgraded to a theme, with Gortyn remaining the administrative, ecclesiastical and economic centre.
In this period there was a settlement identified as Roman Herakleion, which came within the jurisdiction of the Diocese of Knossos. Theodoros, Bishop of Herakleioupolis, is referred to in the Proceedings of the VI Oecumenical Council (786-7) as being third in the hierarchy of the eleven bishops of Crete. By this time Kastro may well have been in use as a place name for the settlement.
The life of the island's inhabitants was determined by developments marking the course of Byzantine society. In the 6th century, Crete was recorded as having 22 towns or sizeable settlements. Over the following century, however, urban centres fell into decline and the population turned to farming. The life of Byzantine farmers in this time was arduous and beset by privation: houses were small, with tiled or thatched roofs, clothing was simple and diet was often limited to vegetables, bread and diluted wine. Natural disasters, epidemics, pirate raids and famine restricted life expectancy to under 45 years of age, combined with a high infant mortality rate. On the eve of the Arab conquest, the population is estimated to have stood between 200 000 and 250 000 inhabitants.
The persecution instigated by various Roman emperors against supporters of the new religion afflicted the Christian community on Crete; the best known instances involved the Ten Martyrs, put to death on 23rd December 250 AD, and Cyril, Bishop of Gortyn, martyred on 9th July 304 AD.
Christianity gained a lasting hold on the island in the 4th century, when the Cretan Church was fully organised.In administrative terms the Archdiocese of Crete was mainly subject to the Patriarchate of Rome, but was annexed once and for all by the Patriarchate of Constantinople in the mid-8th century, with the waning of Byzantine power in Italy, and possibly also on account of the Iconoclast Controversy.
Churches were often adorned with architectural members carved in relief, such as parapets, capitals and impost blocks, following the Hellenistic tradition.
Interior decoration was supplemented by mosaics and wall paintings. During the Iconoclast Controversy, geometric, vegetal and animal designs often symbolic in nature were most common. Following the restoration of the icons in 843, icon art began to emerge along with new types of church, such as the inscribed cruciform basilica with cupola.
The first Arab attack on the island was probably launched in 654, and was followed by several more. Valuable information is given in the life of Saint Andrew of Crete, primate of the Church of Crete from 712 to 740, which relates the following: "The most impious and well-versed in naval warfare of all the Moslems swept across the sea, setting themselves against the island of Crete with many ships, and fear and trepidation possessed the indigenous population and those in the outlying isles..." (Theocharis Detorakis, History of Crete, trans. J.C. Davis, Heraklion 1994, pp. 133).
With excerpts from Heraklion.gr