Description of themata
A theme was a plot of land given to the soldiers to farm. The soldiers were still technically a military unit, under the command of a strategos, a military and civil authority, and they did not own the land they worked as it was still controlled by the state. Therefore for its use the soldiers' pay was reduced. By accepting this proposition, the participants agreed that their descendants would also serve in the military and work in a theme, thus simultaneously reducing the need for unpopular drafts as well as cheaply expanding the military. It also allowed for the settling of conquered lands because these themes could be rapidly formed into military units and there was always a substantial addition made to public lands during a conquest.
Reasons for Heraclian reforms
During the late sixth and early seventh centuries, the Byzantine Empire was under assault. The Sassanid Empire was pressing it from the south and east, assaulting Syria, Egypt and Anatolia. Slavs and Avars raided Greece and disputed the Balkan holdings of the Eastern Roman Empire. The Lombards freely raided northern Italy, completely unopposed. The treasury of the Empire was drained and its generals were in open rebellion. Under such circumstances, Heraclius ascended to the throne and instituted the reforms that would serve as the backbone of the Empire for generations to come.
The reorganizations of Heraclius were sorely needed. With wars being waged simultaneously in the east and the west, the public coffers were all but empty. The problem of increased military expenditures was compounded by peasantry abandoning their lands due to invasions or increased taxes. Population and agricultural production was shrinking in Asia Minor, the empire's power base. Most larger cities were shrinking, with droves of people returning to agriculture in the countryside out of necessity. Furthermore, the empire was relying substantially on mercenaries to fight its wars, a sure sign of weakness. The basic objective of Heraclius’ alterations was to return the military to the republican system of landed citizen armies that had served so well during the initial creation of the Roman Empire. In order to do this, Heraclius began distributing land to the armies and the individual soldiers in exchange for hereditary military duty at a reduced expense to the state.
Outcome of the reforms
This system of transplanting military units into unsettled lands and creating an inherent loyalty to the state, something every government has struggled with, greatly strengthened the Byzantine Empire. Over the next several decades, the Sassanids retreated, the Slavs and Avars were reduced and rebellions within the empire became far less common. The themata military structure rescued the Eastern Roman Empire from destruction and gave it a durability that would last for centuries to come. The price to be paid for this was a general militarization of the society and a decline of civil institutions and civil culture; for this reason, the introduction of themata is seen as marking the end of Late Antiquity and the beginning of the Middle Ages for the Byzantine Empire. However it should be noted that unlike Western Europe, the Byzantine Empire never reduced its farmers to the status of serfs.
Thema system, in time, created aristocratic families such as the Phokas family deeply entrenched in some part of the empire, with what amounted to private armies. These families, having troops loyal to them instead of the emperor and being financially autonomous, often challenged or even usurped imperial authority.
Organization of themata
Heraclius originally divided the existent holdings of the empire into five themata. These were the Armeniac (in 667), the Anatolic (in 669), the Opsician, the Carabisiani and the Thracian (all in 680). The Armeniac thema was originally composed of Pontus and Cappadocia, stretching from Sinope to Trebizond on the Black Sea and extending as far inland as Caesarea (in present-day terms it would comprise the majority of the northeastern quarter of Asiatic Turkey). The Thracian thema was originally composed of a band of territory hugging the coast from Dyrrhachium into Thrace, comprising most of modern Greece, Albania and European Turkey, including Constantinople. The Opsician thema was originally composed of all of Bithynia and Paphlagonia, stretching from Abydos on the Dardanelles to Sinope on the Black Sea and inland to Ancyra (i.e. most of the northwestern quarter of what is now Asiatic Turkey). The southwestern quarter of what is now Turkey was divided between the Anatolic and Carabisiani themata. The Carabisiani thema was narrow band of territory that was comprised of the coastal province of Pamphylia and the isle of Rhodes. The Anatolic thema made a crescent shape arching around Carabisiani, and was originally composed of Lydia, Phrygia, Pisidia and parts of Galatia and Isauria (i.e. an arch of land from Smyrna to Iconium, and then down to the Mediterranean almost as far east as Mersin). These original five themata were later subdivided and new themata were added as the empire pushed outward in the 9th and 10th centuries.
Origins of themata
Each of the original five themata was formed from the Empire's earlier mobile field armies. As the empire had shrunk, most of the armies had retreated to newer stations in the interior. Heraclius assigned each mobile army a part of Anatolia. Because the language of the empire was also being changed from Latin to Greek, the themes acquired Hellenized names.
The Opsician theme was formed from the armies in the Emperor's presence, which had lately been known as the Obsequim (retinue). The armies in the Emperor's presence had been stationed in southern Thrace and northwestern Anatolia, near the capital of Constantinople, and this was where the Opsician Theme was formed.
The Army of Armenia became the Armeniac theme, stationed in most of its original territory in eastern Anatolia, to the west of the Armenian protectorate. The Army of the East, which had formerly defended Roman Syria and Palestine, retreated when those areas were lost first to the Persians and later to the Arabs. They were settled in central Anatolia and became the Anatolic theme. The Army of Thrace became the Thracesian theme, settled in western Anatolia where Heraclius had withdrawn it. Emperor Constans also created a corps of marines, the Carabisian theme, named after a Greek word for ship (karabis) and based in Greece, in the Aegean islands and on the southern shore of Anatolia. This appears to have been formed from the remains of the Army of Illyricum, whose territory had included Greece.
- Warren Treadgold, A History of the Byzantine State and society