Ecology in Ancient Civilizations by J. Donald Hughes

Topsoil and Civilization by Carter and Dale

also just noticed this one on amazon:
A Green History of the World: The Environment and the Collapse of Great Civilizations by Clive Ponting

The first few chapters of Thomas Cahill’s How the Irish Saved Civilization is a stark picture of the fall of the Roman Empire. It is hard to think of a better introduction into the subject. In essence, the wealthy made themselves exempt from taxes which were needed to defend the empire, and the rest of the population were so oppressed and ground down by the curiales, the tax collecting class, that when the barbarians crossed the Rhine and overwhelmed the Roman legions, nobody gave a damn.

Thr Vandals, Alans, and Sueves who crossed over in 406/407 (or 405/406 if you believe Michael Kulikowski) faced a Roman border guard that had been seriously depleted in 402 because Stilicho wanted to use them to fight Alaric. Historians still don’t know why Stilicho didn’t confront the invaders; nor do they know why Stilicho didn’t crush Alaric and his army in 402.

The general public was, by law, unarmed until the Emperor Valentinian III permitted it; but by then it was too late. There was some amount of armed public resistance to the invasions, but not enough.

As for the public being ground down by the tax collectors, historians are sure this happened; but it might have been caused by the invasions themselves, which removed large portions of the Empire from tax collection and thus increased the burden on those who remained.

As he scurried out the door in 2004, Paul Bremer – the first US viceroy to Iraq – issued Order 17, which exempted all mercenaries operating in the country from having to obey the law. He in effect gave these men a licence to kill – and they are using it, every day.

[...]

The US right has a slew of reasons to privatise the US military so rapidly. The most obvious is simple corruption. It funnels money to companies in which they have a huge stake, and who in turn donate a fortune to the Republican Party. This is justified in public by a market fundamentalist conviction that governments can never run anything properly, so their functions must always be sold off.

But this is a secondary motive. The main limit on an aggressive US foreign policy today is the limited number of US citizens who are prepared to kill and die for it. Mercenaries solve the problem: just buy troops in. The public is far less likely to protest against a war if the victims are hardened Colombians in it for the cash, rather than their cousin from Wisconsin who signed up out of patriotism. In mercenary wars, all citizens are asked to give is money, not blood. The Cheney model of mercenary warfare being tried out in Iraq is, in fact, a way of making possible his vision of a 21st century in which wars for resources will be “necessary” on a “regular basis”.

We have been here before. In his Discourses, Niccolo Machiavelli describes how, in its dying days, the Roman Empire was no longer able to inspire a large citizen-militia, and increasingly bought armies of willing foreigners. The result was dissolution, decadence and imperial collapse. What would the world look like if Cheney’s vision of privatised armies prevailed in this century? There would be far more wars, far less checked by the rules of war built up after the nightmare of the 1940s: in other words, more Iraqs.

History also points towards a longer-term danger. Where governments depend on private armies, they become increasingly their servants, physically incapable of standing up to them. In the 14th century, corporations determined the fate of the Hundred Years War, and in lulls in the fighting would burn down towns that refused to pay for their protection. The French sovereign was powerless to stop them, because his own forces were too feeble.

Little more than a century ago, the East India Company ignored the explicit orders of the British government and attacked Portuguese garrisons in India, solely to boost its own profit margins. The Empire relied on private militias, until they slipped off the leash. Phillip Bobbit, a former advisor to presidents Nixon and Reagan, warns in his book The Shield of Achilles that as we dissolve back into private armies, we are setting ourselves up for a repeat of this corporate dominance over government.

Dick Cheney effectively believes in rule by corporations, rather than rule by the state, so for him, this is a comforting vision. [...]

cf US too! Not thinking of Rome here, though at http://www.friesian.com/decdenc2.htm I read:

“The Emperor Heraclius [610 CE] has long been thought to have introduced the innovation of granting small farms to individual soldiers, on the condition of military service, created a system that would ensure not only a supply of military men but also create incentives for productivity on the part of these men who stood to derive all the benefit from their own labor.”

Ah, “productivity” indeed… In an imploding empire domestically there are police forces on a rather loose tether (LAPD, etc); continuing infusions of undercared-for vets whose skill sets are mismatched with living wage jobs in a shrinking economy; minutemen and other vigilante interest groups–that is, groups who can rationalize violence on ideological grounds while pursuing quite material ends.

Globally Blackwater & Titan and other avatars financed at first by states and corporations, but eventually, as their power grows and the power of states dwindles, will begin to locate their own funding and reasons for being.

(The above URL (mostly about language) also talks about the collapse of the cash economy and the resurgence of a mostly barter economy.)

I’m sure there are contingency plans for the use of Blackwater and Titan at home, too.

The 30 Years’ War was made particularly hideous by the roving bands of “freelance” soldiery (ronin) wandering the landscape, looting and raping as they went, loyal to no one but their own “brothers in arms”. When the State loses control of its armed forces it loses its monopoly on violence and ceases to be an organised State… cf Baghdad or Afghanistan today.