The Illyriciani or Illyrian emperors were a group of Roman emperors during the Crisis of the Third Century who hailed from the region of Illyricum (in the Western Balkans), and were raised chiefly from the ranks of the Roman army (whence they are ranked among the so-called "barracks emperors").[1][2]
In the 2nd and 3rd centuries, the Illyricum and the other Danubian provinces (Dacia, Raetia, Pannonia, Moesia) held the largest concentration of Roman forces (12 legions, up to a third of the total army), and were a major recruiting ground. The advance of these low-born provincials was facilitated by a major shift in imperial policy from the time of Gallienus (253–268) on, when higher military appointments ceased to be exclusively filled by senators. Instead, professional soldiers of humble origin who had risen through the ranks to the post of primus pilus (which also entailed admission to the equestrian order) were placed as heads of the legions and filled the army's command structure.
The aims of the Illyrian emperors were roughly identical. Given their low origin, they were opposed to the landowning oligarchy and the senatorial order. Since the security of their birthplace depended on it, they considered the defense of the state's territorial integrity a primary task. They saw this in creating a strict soldier-like discipline (a slogan they frequently glorified on their coins) everywhere. In order to pursue this task, they worked on eliminating privileges and autonomies and subordinating one's interests to the interests of the crumbling empire. Thus, their form of rule was military dictatorship. Paired with vim, the Illyrian emperors' rigid notions led to the rise of the Dominate.[3]
Since Decius hailed from the senatorial background, the historical period of the Illyrian emperors proper begins with Claudius Gothicus in 268 and continues in 284 with the rise of Diocletian and the institution of the Tetrarchy.[4] This period was very important in the history of the Empire, since it represents the recovery from the Crisis of the Third Century, a long period of usurpations and military difficulties. All of the Illyrian emperors were trained and able soldiers, and they recovered most of the provinces and positions lost by their predecessors, including Gaul and the eastern provinces. Men of Illyrian or Thraco-Dacian origin however continued to be prominent in the Empire throughout the 4th century and beyond.
The later Valentinic-Theodosian dynasties (364–457 AD) also hailed from the Pannonia region.