What happened September 282 AD

Carus was apparently a senator and filled various posts, both civil and military, before being appointed prefect of the Praetorian Guard by the emperor Probus in 282. Two traditions surround his accession to the throne in August or September of 282. According to some mostly Latin sources, he was proclaimed emperor by the soldiers after the murder of Probus by a mutiny at Sirmium. Greek sources however claim that he rose against Probus in Raetia in usurpation and had him killed. Bestowing the title of Caesar upon his sons Carinus and Numerian, he left Carinus in charge of the western portion of the empire to look after some disturbances in Gaul and took Numerian with him on an expedition against the Persians, which had been contemplated by Probus.

Probus was eager to start his eastern campaign, delayed by the revolts in the west. He left Rome in 282, traveling first towards Sirmium, his birth city. Different accounts of Probus's death exist. According to Joannes Zonaras, the commander of the Praetorian Guard Marcus Aurelius Carus had been proclaimed, more or less unwillingly, emperor by his troops. Probus sent some troops against the new usurper, but when those troops changed sides and supported Carus, Probus' remaining soldiers assassinated him at Sirmium (September/October 282). According to other sources, however, Probus was killed by disgruntled soldiers, who rebelled against his orders to be employed for civic purposes, like draining marshes. Allegedly, the soldiers were provoked when they overheard him lamenting the necessity of a standing army. Carus was proclaimed emperor after Probus' death and avenged the murder of his predecessor.