"In the various states of society, armies are recruited from very different motives. Barbarians are urged by the love of war; the citizens of a free republic may be prompted by a principle of duty; the subjects, or at least the nobles of a monarchy, are animated by a sense of honour; but the timid and luxurious inhabitants of a declining empire must be allured into the service by the hopes of profit, or compelled by the dread of punishment."

—Edward Gibbon, The Decline and Fall of the Roman Empire Vol. II