Praetorian prefecture

[1] A common misconception, based on Zosimus, is that Constantine I established the praetorian prefectures as definite territorial administrations as early as 318, or in 324, after his victory over Licinius.

Jones, he was "a kind of grand vizier, the emperor's second in command, wielding a wide authority in almost every sphere of government, military and judicial, financial and general administration.

[3] Following Diocletian's abdication in 305, civil war erupted among the various co-emperors, during which time each of the contenders appointed his own prefect, a pattern carried on during the period where the Empire was shared between Licinius and Constantine I.

[8] The office of the prefect was consequently converted into a purely civilian administrative one, albeit retaining the highest position in the imperial hierarchy, immediately below the emperor himself.

This development is likely related to Constantine's giving his four sons specific territories to administer, envisioning a partition of imperial authority among them following his death.

With the creation of the separate prefecture of Illyricum (dioceses of Pannonia, Dacia and Macedonia) in 347 until 361, and despite the occasional abolition of the latter, the picture that appears in the early 5th-century Notitia dignitatum ("list of dignities") was complete.

In the East, the prefectures would continue to function until the mid-7th century, when the loss of most eastern provinces to the Muslim conquest and of the Balkans to Slavic tribes led to the creation of the Theme system.

In the meantime, however, reforms under Heraclius had stripped the prefect from a number of his subordinate financial bureaux, which were set up as independent departments under logothetes.

Their departments were divided in two major categories: the schola excerptorum, which supervised administrative and judicial affairs, and the scriniarii, overseeing the financial sector.

Map of the Roman Empire under the Tetrarchy, showing the dioceses and the four tetrarchs' zones of control.
The administrative divisions of the Roman Empire in 395 AD
The four prefectures of the Roman Empire, as they appear in the Notitia Dignitatum , ca. 400 AD.
The insignia of the praetorian prefect of Illyricum, as depicted in the Notitia Dignitatum : the ivory inkwell and pen case ( theca ), the codicil of appointment to the office on a blue cloth-covered table, and the state carriage . [ 15 ]