Edward Gibbon, The Decline and Fall of the Roman Empire Chp. X Part IV
The rapid and perpetual transitions from the cottage to the throne, and from the throne to the grave, might have amused an indifferent philosopher; were it possible for a philosopher to remain indifferent amidst the general calamities of human kind. The election of these precarious emperors, their power and their death, were equally destructive to their subjects and adherents. The price of their fatal elevation was instantly discharged to the troops by an immense donative, drawn from the bowels of the exhausted people. However virtuous was their character, however pure their intentions, they found themselves reduced to the hard necessity of supporting their usurpation by frequent acts of rapine and cruelty. When they fell, they involved armies and provinces in their fall. There is still extant a most savage mandate from Gallienus to one of his ministers, after the suppression of Ingenuus, who had assumed the purple in Illyricum.
“It is not enough,” says that soft but inhuman prince, “that you exterminate such as have appeared in arms; the chance of battle might have served me as effectually. The male sex of every age must be extirpated; provided that, in the execution of the children and old men, you can contrive means to save our reputation. Let every one die who has dropped an expression, who has entertained a thought against me, against me, the son of Valerian, the father and brother of so many princes. Remember that Ingenuus was made emperor: tear, kill, hew in pieces. I write to you with my own hand, and would inspire you with my own feelings.” Whilst the public forces of the state were dissipated in private quarrels, the defenceless provinces lay exposed to every invader. The bravest usurpers were compelled, by the perplexity of their situation, to conclude ignominious treaties with the common enemy, to purchase with oppressive tributes the neutrality or services of the Barbarians, and to introduce hostile and independent nations into the heart of the Roman monarchy.