In The History of the Decline and Fall of the Roman Empire, published in 1776 in six volumes, the author Edward Gibbon tackles European history. He presents views on religion (Christianity, Islam, Judaism, Paganism), governments within Rome and without (from 198 to 1590 AD), the decline of the Roman military, and the various barbarians that contributed to Rome's ultimate end.

Gibbon's thesis is that Rome did, indeed, fall to invading hordes—as history shows. But he goes farther in analyzing the reasons for this fall, to be found to a weakened state that had overreached itself in its vast territories and colonies. He points to a weakened military that lost its self-discipline, corrupt leadership in the Roman Senate and provinces, an overtaxed lower and middle class, and the rise of various forces such as Christianity that chipped away at the Republic.

It is important to understand the Gibbon wrote about far more than the fall of Rome, the city. He chronicled European history from two centuries after the death of Christ through to Dark Ages, and up to the doorstep of the Age of Reason. He wrote that the Dark Ages were a pause in history, and it could only begin again once his own era (the Age of Reason) was made possible.

His analysis of the Roman military (army and navy) concludes that these branches of the government were, initially, among the best organized on earth. Their systems allowed Rome to conquer other armies through superior organization and size. He also discusses the provinces, from Gallia to Arabia to Africa, and how each was organized and run. Gibbon goes into great detail about how each province was established, run and led in order to create context for a discussion of why, when these systems broke down, Rome disintegrated.

Today, it is well known that Rome's power was due to its scope and ability to govern its provinces. The recruitment of conquered people's into the Roman Empire made for a strong, diverse Republic with a loyal populace. Similar to how the newest immigrants in the U.S. are some of the most patriotic, the provincial people's of Rome loved the advantages of being Roman citizens. In its decline, the provinces had lost effective leadership, overtaxed their citizens, and abandoned their military obligations. Rome's military began to lose its ability to respond to remote crisis due to an erosion of internal discipline and the prevalence of civil unrest.

In the second half of this ambitious history, Gibbon discusses the fall of another great civilization, Constantinople. He chronicles the Justinian age and the emergence of Islam on the world stage. Unlike other writers, Gibbon pulls no punches when it comes to religion, and reveals Mohammed (the prophet of Islam, analogous to Christ as the prophet of Christianity) to be a mere mortal who indulged in wine and sex.

Gibbon's thesis is that Rome overreached herself under Augustine. The Roman Empire was vast, but in continuing to conquer new territory its public administration reached a limit and was unable to sufficiently govern. Once the government began to show cracks, it became vulnerable to external threats. The once powerful and well-organized armies and navies, for example, got caught up in settling civil wars. The quality of soldiers declined (particularly the higher quality field force), a draft was never implemented, and deferments from service for senators and other "connected" individuals became commonplace. Both the quality and size of the army was thus diminished.

The military lost much of its power due to a lack of support from Roman society. Rome and its military had a symbiotic...