the Central Lowlands. This is evidenced by extensive Severan-era fortifications in the Central Lowlands. The Caledonians, short on supplies and feeling that their position was desperate, revolted later that year with the Maeatae. Severus prepared for another protracted campaign within Caledonia. He was now intent on exterminating the Caledonians, telling his soldiers: "Let no-one escape sheer destruction, no-one our hands, not even the babe in the womb of the mother, if it be male; let it nevertheless not escape sheer destruction." Death (211) Severus' campaign was cut short when he fell ill. He withdrew to Eboracum (York) and died there in 211. Although his son Caracalla continued campaigning the following year, he soon settled for peace. The Romans never campaigned deep into Caledonia again. Shortly after this, the frontier was permanently withdrawn south to Hadrian's Wall. Severus is famously said to have given the advice to his sons: "Be harmonious, enrich the soldiers, scorn all others" before he died on 4 February 211. On his death, Severus was deified by the Senate and succeeded by his sons, Caracalla and Geta, who were advised by his wife Julia Domna. Severus was buried in the Mausoleum of Hadrian in Rome. Assessment and legacy By the close of his reign the Roman Empire reached an extent of over million square kilometres, which scholars like David L. Kennedy, Lukas de blois, and Derrick Riley state expanded the empire to its greatest physical extent. Edward Gibbon famously levelled a harsh indictment of Septimius Severus as a principal agent in the empire's decline. "The contemporaries of Severus, in the enjoyment of the peace and glory of his reign, forgave the cruelties by which it had been introduced. Posterity, who experienced the fatal effects of his maxims and example, justly considered him as the principal author of the decline of the Roman empire." According to Gibbon, "his daring ambition was never diverted from its steady course by the allurements of pleasure, the apprehension of danger, or the feelings of humanity." His enlargement of the Limes Tripolitanus secured Africa, the agricultural base of the empire where he was born. His victory over the Parthian Empire was for a time decisive, securing Nisibis and Singara for the empire and establishing a status quo of Roman dominance in the region until 251. His policy of an expanded and better-rewarded army was criticised by his contemporaries Cassius Dio and Herodianus: in