Complexity and Collapse - Niall Ferguson

>http://www.foreignaffairs.com/articles/65987/niall-ferguson/complexity-and-collapse?page=6
Excerpt -

Defeat in the mountains of the Hindu Kush or on the plains of Mesopotamia has long been a harbinger of imperial fall. It is no coincidence that the Soviet Union withdrew from Afghanistan in the annus mirabilis of 1989. What happened 20 years ago, like the events of the distant fifth century, is a reminder that empires do not in fact appear, rise, reign, decline, and fall according to some recurrent and predictable life cycle. It is historians who retrospectively portray the process of imperial dissolution as slow-acting, with multiple overdetermining causes. Rather, empires behave like all complex adaptive systems. They function in apparent equilibrium for some unknowable period. And then, quite abruptly, they collapse. To return to the terminology of Thomas Cole, the painter of The Course of Empire, the shift from consummation to destruction and then to desolation is not cyclical. It is sudden.