Main Byzantine period (7th century - 13th century A.D.)
The prosperous early byzantine period, during which the life of the ancient Thessalian cities continues up to a point, slightly differentiated due to the influence of Christianity, is interrupted around the end of the 6th A.C., by a long period of turbulence and unrest, during which the cities of Thessaly are no longer mentioned in the scriptures.
This phenomenon, which is caused mostly by barbaric raids, affects up to a certain degree the remaining provinces of the byzantine empire, that' s why the 7th and 8th c. are called «dark ages». Great tumult is caused by the raids of Slavic races, part of which settle permanently in areas of Thessaly and Makedonia. The exact details of the time and place of their settlement are unknown, but one of those, the Velegezites, are placed around the 8th c. at the coasts of the Pagassitikos gulf. With the appropriate policy of the byzantine emperors, the Slavs are christianised and gradually integrated into the local population.
Following the administrative reorganisation of the state, to deal with the new dangers, Thessaly belongs to the Greek Issue, which initially includes only the region of central Greece and later spreads to the south. At various times Larissa was the capital of the Issue, especially during the Bulgarian wars
In the 8th c. the sources become confused in relation to the name of Thessaly, since that term is by now used for Thessaloniki and present day Thessaly is referred to as Deftera Thessaly (= Second Thessaly), while from the 12th c. onwards it is often mentioned as Vlachia of Megali Vlachia.
In the 10th c. more devastating raids are carried out in Thessaly. In one of these, 901/2 A.D. was associated with the Arabs.
After that, Thessaly is seriously threatened by the successive raids of the Bulgarians, which reach their apex during the last two decades of the century, with the conquest of Larissa in 982 by czar Samuel, after a three-year siege and capture of its inhabitants. During that time, the remains of Saint Achillios were relocated from Larissa to Prespa, where a church was built in his name.
For many years the whole region suffered greatly until general Nikiforos Ouranos defeated the Bulgarians in 996, during the battle of the Sperhios. A period of peace followed, during which emperor Vassilios II reorganised the Byzantium and amongst other things reconstructed the destroyed fortresses of Thessaly
The flourishing Early Byzantine period, in which is continued the life of ancient Thessalian cities to a certain point (differentiated however under the effect of Christianity), is interrupted by an enduring period (from the end of 6th century A.D.) of many disturbances and agitations, where cities of Thessaly cease to be reported in the historical sources.
The next grave danger for Thessaly appeared during the time of emperor Alexios I Komninos (1081-1118), when the Normans marched against it. The leader of the Normans, Bohemund, raided the region and laid siege to Larissa for an extended period, but was successfully turned back by Alexios in 1083.
From the 12th c. and mostly from the following period, the degradation of the central organisation of the state starts to become apparent as does the appearance of small districts with various names, a system particularly popular in Thessalia with the vast plains and fertile lands, which attracted the interest of the powerful of the period. The visit of Reveniko and Farsalos, the province of Vlachia, the visit of Domokos and Vessena and others that in 1204 were owned by the empress wife of Alexios III Komninos, are also mentioned.
References in Greek language:
Σδρόλια Στ., Δρ Βυζαντινής Αρχαιολογίας -(Sdrolia S. PhD in Byzantine Archaeology), Αρχαιολόγος 7ης ΕΒΑ. ΤΕΔΚ Νομού Λάρισας, Οδηγός Νομού Λάρισας, Λάρισα 1998
ΤΕΔΚ Νομού Λάρισας, Οδηγός Νομού Λάρισας, Λάρισα 1998