http://www.opednews.com/articles/Empires-Then-and-Now-by-Paul-Craig-Roberts-120327-813.html

March 27, 2012

Empires Then and Now

This article cross-posted from Paul Craig Roberts IPE

Great empires, such as the Roman and British, were extractive. The empires succeeded, because the value of the resources and wealth extracted from conquered lands exceeded the value of conquest and governance. The reason Rome did not extend its empire east into Germany was not the military prowess of Germanic tribes but Rome's calculation that the cost of conquest exceeded the value of extractable resources.
The Roman empire failed, because Romans exhausted manpower and resources in civil wars fighting amongst themselves for power. The British empire failed, because the British exhausted themselves fighting Germany in two world wars.