Gibbon on the Military

In discussing the raising of Roman armies around the time of Constantine in The Decline and Fall of the Roman Empire, Gibbon says:

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 sentiment 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.

Unfortunately the last category seems to apply to the US military from Vietnam up to today in Iraq. Gibbon goes on to describe a situation not very different from today's America, trying to maintain a relatively small army in Iraq:

The resources of the Roman treasury were exhausted by the increase of pay, by the repetition of donatives, and by the invention of new emoluments and indulgences, which in the opinion of provincial youth, might compensate the hardships and dangers of a military life. Yet, although the stature was lowered, although slaves, at least by a tacit connivance, were indiscriminately received into the ranks, the insurmountable difficulty of procuring a regular and adequate supply of volunteers obliged the emperors to adopt more effectual and coercive methods.