Fantasy and sci-fi are chock full of fallen, lost, or otherwise no longer present civilizations. They’re as much a staple as elves, dwarves, warp drive, and droids. So, how do civilizations fall? And, do how often do they completely die out?
We know civilizations can completely die out. We have evidence for this throughout Mesopotamia. However, in the last 3,000 years, the number of totally wiped out civilizations (in the Western world at least) is practically zero.
Also, there is rarely a clear cut end date for empires. To the best of my knowledge, there is nothing in history like the dramatic end of Atlantis (one night of destruction). Obviously, this doesn’t mean such and end can’t exist in fantasy or SF. But, when every civilization falls or dies that way, it gets a bit old and loses dramatic effect.
Most, if not all, empires and civilizations end up dwindling away with a whimper.
I’m going to use the Roman Empire, the British Empire, the Mongolian Empire, and medieval France to illustrate both why empires fall and how they often continue on as civilizations for centuries after their imperial demise.
Medieval France presents a perfect example of a factor in the death of an empire: government. In the case of medieval France, lack of a strong central government nearly killed the kingdom before it really began. For much of its medieval history, French government was dispersed among the nobles. Each noble governed his own territory. The king was basically a noble with more responsibility, a fancy title, and no more power than any other noble. The French king really only controlled the land around Paris. His authority only extended as far as his knights could reasonably ride to enforce his edicts. Beyond a day’s ride or so from the city, the king had no power. And France’s neighbors took advantage of this decentralized power, as did the Vikings (who sacked Paris multiple times).
The Mongolian Empire perhaps the three biggest things that allowed the Mongolian Empire to exist were its excellent communication/postal system, tactics and strategy, and its firm central government. On the other hand, its hidebound customs and relative inability to change with the times led, I think, to its downfall. The primary custom that needed to change was the election of new rulers. When every general needs to return to the capital to vie for the top spot, it causes problems. Were it not for Genghis’ death, the Mongols may have made greater strides into Europe. But, the empire never recovered its momentum after Genghis’ death. That said, it still took a few generations for the empire to completely fall and even so the civilization never died out, as evidenced by the Mongols’ return to the largely herding culture of their forefathers that is still alive and still called Mongolia today.
The British Empire, I think, largely collapsed for two major reasons (and a whole host of others). Perhaps the most important is the force of history. Cultural changes and the aftereffects of WWII led to a shift in views and ethics, particularly amongst those who had formerly made up the colonial police and British military. Those shifts tended toward anti-colonialism (in Britain, France, and elsewhere). Combined with this change in views came the realization of just how unsustainable, in terms of finances and manpower, a military empire is (e.g. the cost of maintaining a global navy, army, and colonial police). Add in the post-WWII distaste for war that creeped through Europe, and there’s a recipe for the end of the empire. Obviously, those, the empire was not dismantled overnight (in fact, there are still colonies and the queen is still technically the Canadian head of state), nor did British civilization die out. It merely changed, adapted, evolved.
The Roman Empire fell, some claim, due to the “bread and circuses”, but I don’t think this is really true. They may have been a factor, but if so, I think they were a minor factor. Instead, I think there were four major factors that ultimately led to the empire’s fall. First, the Romans reached the geographical limits of their technology, then tried to push farther. The key technology in this case being communications. Unlike the Mongols, they never set up anything like a high speed communication service. This led to the creation of two capitals, which decentralized governance and power, and hastened the cultural divide between the eastern and western empires. Additionally, lack of speedy communications meant that the emperor and senate rarely had up to date information about events along the empire’s borders (such as Britain). Tied to this was the empire’s need for continual expansion. In order to maintain its standing army and the bureaucracy necessary for a nation of its size, the Roman Empire had to keep expanding, conquering new territory (and thus bringing in more taxpayers and more spoils of war). That’s a non-sustaining system. On a related note, the army that kept expanding the empire and kept the peace was eventually a non-citizen army (sometimes fully mercenary). In time, only the officers were Roman citizens and service in the legions was a path to citizenship. Of course, it could be easier for the soldiers to simply take citizenship by force, which some legions did occasionally. Finally, from what I recall from a civ course many years ago, many of the Roman emperors, particularly the later ones, spent most of their time looking backward to a fictional, idealized, glorious Rome of yesteryear. They kept trying to put in place legislation regarding morality, to bring things back to the “good old days” and such. Instead, they should have been looking forward, toward the future (as many of the good emperors did) and living in the present.
I don’t claim to be an expert on history and the above thoughts are a gross simplification, but they are the conclusions I’ve drawn from a fair bit of research and reading. Whether true or not for our world, perhaps they’ll spark some imaginations for someone’s world building.