was Roman Dacia's military center. The region was soon settled by the retired veterans who had served in the Dacian Wars, principally the Fifth (Macedonia), Ninth (Claudia), and Fourteenth (Gemina) legions. While it is certain that colonists in large numbers were imported from all over the empire to settle in Roman Dacia, this appears to be true for the newly created Roman towns only. The lack of epigraphic evidence for native Dacian names in the towns suggests an urban–rural split between Roman multi-ethnic urban centres and the native Dacian rural population. On at least two occasions the Dacians rebelled against Roman authority: first in 117 AD, which caused the return of Trajan from the east, and in 158 AD when they were put down by Marcus Statius Priscus. Some scholars have used the lack of civitates peregrinae in Roman Dacia, where indigenous peoples were organised into native townships, as evidence for the Roman depopulation of Dacia. Prior to its incorporation into the empire, Dacia was a kingdom ruled by one king, and did not possess a regional tribal structure that could easily be turned into the Roman civitas system as used successfully in other provinces of the empire. As per usual Roman practice, Dacian males were recruited into auxiliary units and dispatched across the empire, from the eastern provinces to Britannia. The Vexillation Dacorum Parthica accompanied the emperor Septimius Severus during his Parthian expedition, while the cohort I Ulpia Dacorum was posted to Cappadocia. Others included the II Aurelia Dacorum in Pannonia Superior, the cohort I Aelia Dacorum in Roman Britain, and the II Augusta Dacorum milliaria in Moesia Inferior. There are a number of preserved relics originating from cohort I Aelia Dacorum, with one inscription describing the sica, a distinctive Dacian weapon. In inscriptions the Dacian soldiers are described as natione Dacus. These could refer to individuals who were native Dacians, Romanized Dacians, colonists who had moved to Dacia, or their descendants. Numerous Roman military diplomas issued for Dacian soldiers discovered after 1990 indicate that veterans preferred to return to their place of origin; per usual Roman practice, these veterans were given Roman citizenship upon their discharge. In an attempt to fill the cities, cultivate the fields, and mine the ore, a large-scale attempt at colonization took place with colonists coming in "from all over the Roman world". The colonists were a heterogeneous mix: of the some 3,000 names