Part I
Under the deplorable reigns of Valerian and Gallienus, the empire was oppressed and almost destroyed by the soldiers, the tyrants, and the barbarians. It was saved by a series of great princes, who derived their obscure origin from the martial provinces of Illyricum. Within a period of about thirty years, Claudius, Aurelian, Probus, Diocletian and his colleagues, triumphed over the foreign and domestic enemies of the state, reestablished, with the military discipline, the strength of the frontiers, and deserved the glorious title of Restorers of the Roman world.
The removal of an effeminate tyrant made way for a succession of heroes. The indignation of the people imputed all their calamities to Gallienus, and the far greater part were indeed, the consequence of his dissolute manners and careless administration. He was even destitute of a sense of honor, which so frequently supplies the absence of public virtue; and as long as he was permitted to enjoy the possession of Italy, a victory of the barbarians, the loss of a province, or the rebellion of a general, seldom disturbed the tranquil course of his pleasures. At length, a considerable army, stationed on the Upper Danube, invested with the Imperial purple their leader Aureolus; who, disdaining a confined and barren reign over the mountains of Rhaetia, passed the Alps, occupied Milan, threatened Rome, and challenged Gallienus to dispute in the field the sovereignty of Italy. The emperor, provoked by the insult, and alarmed by the instant danger, suddenly exerted that latent vigor which sometimes broke through the indolence of his temper. Forcing himself from the luxury of the palace, he appeared in arms at the head of his legions, and advanced beyond the Po to encounter his competitor. The corrupted name of Pontirolo still preserves the memory of a bridge over the Adda, which, during the action, must have proved an object of the utmost importance to both armies. The Rhaetian usurper, after receiving a total defeat and a dangerous wound, retired into Milan. The siege of that great city was immediately formed; the walls were battered with every engine in use among the ancients; and Aureolus, doubtful of his internal strength, and hopeless of foreign succors already anticipated the fatal consequences of unsuccessful rebellion.
His last resource was an attempt to seduce the loyalty of the besiegers. He scattered libels through the camp, inviting the troops to desert an unworthy master, who sacrificed the public happiness to his luxury, and the lives of his most valuable subjects to the slightest suspicions. The arts of Aureolus diffused fears and discontent among the principal officers of his rival. A conspiracy was formed by Heraclianus the Praetorian praefect, by Marcian, a general of rank and reputation, and by Cecrops, who commanded a numerous body of Dalmatian guards. The death of Gallienus was resolved; and notwithstanding their desire of first terminating the siege of Milan,