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 (the modern Western Balkans), and were raised chiefly from the ranks of the Roman army (whence they are ranked among the so-called "barracks emperors"). In the 2nd and 3rd centuries, the Illyricum and the other Danubian provinces (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 (260–268) on, when higher military appointments ceased to be exclusively filled by senators. Instead, professional soldiers of humble origin who