Theme (Byzantine district)

[2] Justinian also endowed governors (eparchs, stratelates) of the eastern provinces plagued by brigandage and foreign invasions with military and administrative powers, formally abolishing the empire's dioceses, Diocletian's main administrative structure, but more importantly, he had also created the exceptional combined military-civilian circumscription of the quaestura exercitus and following the norm, abolished the Diocese of Egypt putting a dux (Greek: stratelates) with combined authority at the head of each of its old provinces instead.

The rapid Muslim conquest of Syria and Egypt and consequent Byzantine losses in manpower and territory meant that the Empire found itself struggling for survival.

As established by Hellenistic political practice, philosophies and Orthodox doctrines, power had been concentrated in military leaders strategoi who acted as viceroys in their respective "théma", being appointed by the emperor alone.

[5] The remaining imperial territory in Asia Minor was divided into four large themes, and although some elements of the earlier civil administration survived, they were subordinated to the governing general or stratēgos.

[9] Most notable amongst the supporters of this thesis was George Ostrogorsky who based this opinion on an extract from the chronicle of Theophanes the Confessor mentioning the arrival of Heraclius "in the lands of the themes" for the year 622.

In his view, instead of the old force, heavily reliant on foreign mercenaries, the new Byzantine army was based on native farmer-soldiers living on state-leased military estates (compare the organization of the Sasanian aswārān).

[7][13] More recent scholars however have posited that the formation of the themes did not constitute a radical break with the past, but rather a logical extension of pre-existing, 6th-century trends, and that its direct social impact was minimal.

The Thracesian Theme (Θέμα Θρᾳκησίων, Théma Thrakēsiōn), first mentioned clearly as late as c. 740, was the successor of the Army of Thrace, and covered the central western coast of Asia Minor (Ionia, Lydia and Caria), with its capital most likely at Chonae.

[20] In addition, the great naval division of the Carabisians or Karabisianoi (Kαραβισιάνοι, "people of the κᾱ́ρᾰβοι [ships]"), first mentioned in 680, was probably formed of the remains of the Army of the Illyricum or, more likely, the old quaestura exercitus.

[21] In the event, the Carabisians would prove unsatisfactory in that role, and by 720 they had been disbanded in favour of a fully fledged naval theme, that of the Cibyrrhaeots (Θέμα Κιβυρραιωτῶν, Thema Kibyrrhaiotōn), which encompassed the southern coasts of Asia Minor and the Aegean islands.

[27] Sicily too was formed as a theme by the end of the 7th century, but the imperial possessions in mainland Italy remained under the exarch of Ravenna or the local doukes, as did Byzantine Africa until the fall of Carthage in 698.

[31] This process, resulting in unified control over both military and civil affairs of each theme by its strategos, was complete by the mid-9th century,[32] and is the "classical" thematic model mentioned in such works as the Klētorologion and the De Administrando Imperio.

At the same time, the need to protect the Anatolian heartland of Byzantium from the Arab raids led to the creation, in the later 8th and early 9th centuries, of a series of small frontier districts, the kleisourai or kleisourarchiai ("defiles, enclosures").

The term was previously used to signify strategically important, fortified mountain passages, and was now expanded to entire districts which formed separate commands under a kleisourarchēs, tasked with guerrilla warfare and locally countering small to mid-scale incursions and raids.

Most consisted merely of a fortress and its surrounding territory, with a junior stratēgos (called zirwar by the Arabs and zoravar by the Armenians) as a commander and about 1,000 men, chiefly infantry, as their garrison.

[40] The Komnenian era saw a brief restoration of the empire's fortunes as the force now known as the 'Komnenian army' was established by Alexios I Komnenos, marking a decisive break with the thematic system.

The governorships were specifically reserved for relatives of the Komnenian family alone and though efficient emergency measures, it successfully turned the empire into a dependency on foreign mercenaries, yielding the mass of native Greeks and making it unprecedentedly subordinate to the will of its European counterparts.

The pronoiars became the bulk of the imperial tagmata's reserves, slowly taking their place side by side with the totally lawless landed monasteries and the dynatoi, who after Alexios's tax reforms could formalize the various illegally acquired towns and communes as long as they could secure the full taxation of their new domains by the fisc, a process worse fueled by the extensive chrysobulas of different institutions granted by the monarch.

[43][44] The Byzantine army of the Komnenian era never managed to field the manpower of the themes in their heyday, and the new system proved more expensive to maintain in the long run.

The now irrelevant micro provinces under imperial control were organized directly into katepanakias or kephalatikion each also ruled by a Katepan or Kephale with military and civic powers centered around forts and major passes, relegating all minor tasks to deputies.

A theme was an arrangement of plots of land given for farming to the soldiers "stratiotai" coexisting with different villages and towns, "Komai", "Chora" which were taxed for rapid and continuous revenue for the state with an easy and simple handling for a more direct control of the empire by the emperor alone or his viceroys, which ultimately, was a simplified Hellenistic and fiscal administrative principle adapted for war times.