Answer
Severus was proclaimed emperor by the legions in 193, following the assassination of the emperor Pertinax. The Praetorian Guard had sold the throne to the highest bidder, Didius Julianus, which sparked outrage among the troops outside Rome who felt they should have the privilege to choose the emperor. Severus marched on Rome and forced Didius to abdicate within months of his reign, becoming the first emperor from Africa.