The assassination of Commodus (192), followed in less than three months by the murder of his excellent successor, Pertinax, and by the sale of the imperial dignity to the highest bidder, introduced a dreadful period of civil war in which the whole empire had nearly fallen asunder in ruin. Of the three candidates for the purple, Pescennius Niger in Syria, Albinus in Britain, and Septimius Severus on the Middle Danube, Severus, who had the advantage of being nearest to the capital and was therefore first acclaimed as emperor, was also at last the victorious one, but he had a hard fight, especially with Albinus, who led the three legions which still composed the army of Britain to a bloody battle in the plains of Lyons. The confusion of the times and the absence of the Roman legions were undoubtedly favourable to the restless barbarians. The wall of Hadrian was broken through; the Mæatæ, who lived immediately to the north of it, burst into the province, and the governor, Virius Lupus, purchased a precarious peace by paying a large sum to the invaders. It may be easily imagined that the condition of Britain after such an ignominious conclusion of a campaign, and even after the return of the disaffected legions of Albinus, was far from satisfactory, but it was apparently not till 208 that Septimius Severus set forth from Rome to bring the affairs of the province into order. He was already more than sixty years of age, his joints were racked by gout and his heart was sore through the fierce dissensions of his two sons, Caracalla and Geta, and the evils which these foreboded for the empire. Yet even these dissensions urged him the more to undertake the expedition, for he hoped that common labours and common dangers might in some degree tend to draw the two hostile brothers together, and that the necessary hardships of a camp life under our northern skies might restore some of the moral tone which had been lost amid the vicious indulgences of Rome. In this hope, it is true, he was completely disappointed. The hatred of Caracalla, especially for his brother, waxed fiercer and fiercer, and included also his father, for whose death he longed with scarcely concealed eagerness. Borne in his litter, on account of his sufferings from gout, the brave old soldier traversed the greater part of Caledonia, hewing down forests and throwing causeways across marshes; slaying, of course, multitudes of barbarians, but losing also 50,000 of his own troops (so we are told, but the estimate is probably exaggerated) by hostile ambuscades, severities of weather, even by the swords of his own soldiers, who often killed their own comrades to prevent their falling into the hands of the barbarians. He had a mind, too, to explore the secrets of Nature, and compared with wonder the all-but perpetual day of midsummer and the scanty measure of light at midwinter in northern Scotland.