I was reading a book on the Byzantine Empire, and at its height it controlled much of the Mediterranean. I looked up the Arabs and saw that at the dawn of Islam they built an empire that lasted for a short time stretching from Spain to China and India. It began to break up after reaching a certain size, though. The Mongol Empire conquered everything from China to Poland and it was divided into several smaller Mongol ruled empires because Genghis Khan's descendants realised the empire was too big.

My question is:

Over many generations, how large could an Empire with Early to Middle Medieval technology get before collapsing due to communication problems, rebellions, economic problems, tyrannical leaders, and enemy incursions?

Assume that this Empire relies mainly on taxing trade for income, and that many of the surrounding nations hate it because of its riches (causing wars that this empire, which we will call Imperium for now, wins due to the technological edge.

Also, assume that it only mildly incorporates Feudalism (e.g. having land granted to knights, but those knights cannot legally have vassals of their own, which will dramatically limit the breakup of central authority).

  • $\begingroup$ Would you count the Holy Roman Empire as a single political entity? It was quite large but could only survive because of a very laissez-faire government style in regards to the feudal lords below it giving it not much de-facto political power. $\endgroup$ – Philipp Mar 23 '15 at 22:12
  • $\begingroup$ @Phillip I don't think it really counts as an Empire...... I should include that my definition of an Empire is a centralized government headed by an Emperor/King that [usually] inherits the throne through heredity that governs many different cultures and ethnicities. The HRE was more of an extremely primitive Democracy as the feudal lords elected the Emperor who ruled for life----the title of Emperor was usually not hereditary. $\endgroup$ – JDSweetBeat Mar 24 '15 at 12:49
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    $\begingroup$ How medieval? By the tine the Philippines went under Spanish control, the technology wasn't much different from that available in the Middle Ages. And that's about the highest communication lag with respect to the center that I'm aware of for any historical empire (even more than you'd expect from a glance on a world map, because communication from the Philippines actually went through Peru). $\endgroup$ – January First-of-May Mar 13 '16 at 9:38
  • $\begingroup$ @January First-of-May - The Philippines actually communicated through Mexico. They were part of the Vice royalty of New Spain with its capital at Mexico City, which in turn was part of the Kingdom of the East and the West Indias, a crown land of the crown of Castile. $\endgroup$ – M. A. Golding Mar 2 '18 at 0:04

There is no hard limit, it really depends on the geography, administration and history of the empire.

The first main factor is the ability of the empire to decentralize administration (in the EU I think it is called Subsidiarity principle) and the basic principle was known and used by large empires in ancient times. The Persians, the Romans, and the Chinese all used decentralization to manage large empires. As the central power weakens the empire gets unstable and satraps, governors, local kings, or whatever, will rebel, but in times of strong central power the system was proven to work well enough.

How large an empire the system can support depends on how strong the bureaucracy and the tradition of the empire are in relation to the ambition of a strong charismatic leader. The empires I mentioned had very strong grip on being the source of legitimate authority in their region. Kings were claiming the title of the Roman emperor centuries after it was actually relevant because of the prestige. Similarly Chinese dynasties had strong continuity even then the new dynasty was originally of foreign origin.

Communication lag is also critical. Large empires put high priority on good communications. The Roman and British empires were built around sea travel. The Romans and Persians built great roads to connect their empire. The Chinese built great canals. This is where geography matters.

Generally as long as there is no external threat the empire can't handle and the administration does not collapse from within, the empires survived well enough. The issue is that if there is an external threat, responding to attacks efficiently becomes progressively more difficult the larger the empire is. Eventually the local forces responsible for defense will have so much autonomy they will become independent countries in practice, although they will generally remain nominally loyal as long as the administration is stable. Having the support of the emperor had very real political value, even if you were actually independent.

Note that the British empire had areas all over the world with very large communication lags. This was possible because in colonialism the ruling elite was attached to the homeland, not to the people and land they administrated. This obviously sucked for the people being ruled, but allows very large empires. The Chinese had similar system based on centralized system of imperial examinations. The Romans did a good job of attaching the provincial elites to the Roman politics and civilization. So good that much of the areas they romanized still speak languages derived from latin. The Persians also were good at this, and a good source to copy as their approach of winning popular support by protecting local religions resonates well with modern people.

Another simple solution used by great empires was "divide et impera". If your administrative units are too weak to rebel successfully and like you better than each other... Your empire can grow very large. I could mention the usual suspects as examples, but there is no point, really.

Fundamentally, the Persians, the Romans, and the Chinese stopped expanding because they chose to do so. The Persians could have annexed Greece in its time of weakness before rise of Macedonia. The Romans had an edge over the Parthians and could have taken Germany back if they chose to. The Chinese could have usually taken Korea, Japan, or any of their neighbours, really.

So why didn't they? Well, once the distance from capital becomes large enough, you either go along the army and lose effective control of your empire for the duration of the war or give some ambitious and competent general control of a powerful military force you can't effectively control. Neither is really very appealing option. When you factor in that the potential profit becomes smaller in relation to potential loss, the larger the empire becomes, it is easy to understand why large empires simply claimed to rule the world instead of actually trying to do so.

The natural borders for a large empire are therefore areas of low value or large opponents that would require large army to defeat. In either of those cases the gain does not justify the potential losses.

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This also has a lot to do with the speed of communication, speed and ability to transport material goods, and social homogeneity of its peoples.

The longer it takes to communicate, or transport goods, with the farthest reaches of your dominion, the more autonomous it naturally becomes. Greater autonomy means less reliance on the distant, central government.

Geography, bureaucracy, technology all help decide how fast communication crosses the empire.

Social Homogeneity... There are a few modern examples showing that a socially mixed group fosters political factions: the EU, United States, Jerusalem. As a political and financial collective of countries it is worth putting in this list because a collective of confederate countries is a political pathway toward a unified political system. However, the EU is having trouble maintaining cohesion because of member countries like Greece. Greece has a separate social, political and financial approach when compared to countries like Germany. Greece isn't only financially unable to support itself, but often times seems socially unable to right its own financial practices. This is hard on Greece, AND it threatens the strength of the EU because agreed rules and practices are not being met.

The United States is an excellent candidate when discussing political unrest due to a socially heterogeneous collective. To this day, the country faces ideological fighting from its civil war: the systemic racism in politics and government, the growing animosity in a political discourse that has no apparent reason for it, and the fight over a Southern flag and what it means even 150 years later. While it's easy to say that America doesn't fit in this discussion because it's still a unified country, the amount of political rhetoric about various states seceding from the Union gives a non-trivial hint that all is not well - despite the country having suffered worse. A look at the origins of the US will also show that it was formed because a few key conditions were met. The time to communicate with the central government was so slow that the Crown purposefully established governors to act on its behalf. A few generations in and all the governors were now local born citizens of colonies who were more aware of the troubles of the colonists than of the Crown. They were rooted in the community, not the Crown.

The ability to ship goods was slow, and therefore expensive, this forced the colonists to become self-reliant, again making the generations of colonists more aware of their problems as farmers and providers, then of the problems of the the distant and absent economic presence of the Crown. The colonists were allowed to become more self-sufficient because of the access to material goods at their hands. This unique circumstance also worked against the strength of the Crown.

Jerusalem has, for thousands of years, been a land of contested ownership, with the major Abrahamic religions warring each other over control. Even now, the city is split, like Berlin was after WW2. Like Jerusalem, Berlin (and therefore Germany) was controlled by political groups with cross purposes. In fact, I think we can say that much of the Middle East is at a constant war whether the war come in the form of political, martial, ideological or financial methods. With these wars, and these factious beliefs, there can be no unifying political or social body.

Speed of Communication and Transport... The size of the known world, and the speed of light, both relate to a political entity's communication. These also relate to technology, geography and bureaucracy.

There was a time when the peoples Europe and Asia believed that the world ended with them. To explore meant to send ships, if they had ships. Simply, there was a time before ships which greatly impeded travel which necessarily impeded communication and transportation. Fine, so ships came along. But they weren't really great ships at first, and definitely not technologically sound enough to travel the oceans and do so reliably. How could anyone navigate when the clouds hid the night stars? How could they accurately tell time, to measure distance, even if the stars were out? These missing technologies caused many adventurers to go missing therefore making communication and transportation unreliable.

So, fast forward a few hundred years. Now, we have accurate naval time pieces and GPS and satellites and cell phones and such. All this means is that we are better able to colonize farther reaches. But, we're still hindered by the very fabric of the universe itself. If we were to talk on the phone and experience a delay between speaker and listener, of more than a half second then we would become irritated therefore making it less likely that we would talk. It would take effort and patience and live communication wouldn't be spontaneous. It would become a series of reports, or a Q&A, and a pre-planned one. This delay in communication only gets worse as we start to imagine an empire that spans neighbors in a single solar system. Imagine a half hour delay between speaker and listener as we talked to a friend on the nearby planet. Now, imagine running a full parliamentary procedure that involved a teleconference with that neighboring colony. To be sure, that neighboring colony would need a political figurehead, like a governor, to oversee the daily operations of the business of the pan solar collective. Of course, now the local figureheads and colonies are being discussed, we come back to a very old problem in social segmentation... autonomy via self-reliance and self-identification (ie. Us vs them). Technologically, how do you slow this erosion of political influence? Increase technology or keep like minded colonists on your planets and rotate them out occasionally.

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  • $\begingroup$ Thanks for the answer. Would you mind expanding on it though? It just does not feel complete. $\endgroup$ – JDSweetBeat Nov 9 '15 at 19:14
  • $\begingroup$ This would make a good answer if you can expand it some more. $\endgroup$ – bowlturner Nov 9 '15 at 19:22
  • $\begingroup$ Will do. I'll update later today with more information. $\endgroup$ – Andrew Nov 9 '15 at 19:31
  • $\begingroup$ Updated my answer $\endgroup$ – Andrew Nov 10 '15 at 22:11

The splits in the Mongol empire were due to wars of succession amongst Genghis Khan's descendants.

Genghis Khan himself was a spectacularly effective empire-builder because of the basic principle followed earlier by the Romans. Once you've conquered your enemy militarily, you don't put your own people in place to rule them, and expand your laws everywhere. Or if you are going to put your laws in place, you make sure it's for things which everyone agrees on. (The saying goes that a virgin girl could walk unmolested the length of the empire, for example; at least until she met Khan himself anyway!) Instead, you put in one of their own people at the top of the local feudal hierarchy, and you let them run things their way. So long as they're sending you taxes and they aren't trying to rebel, you basically leave them to it. In your own administration (Khan was illiterate) you put people in place to do the stuff you can't do, and to run things day-to-day for you.

In other words, basically you invent middle management.

In the meantime, by the rulers having better conditions than everyone else, and trade being opened up, you make sure that all these new people want to be like you. The empire stops the neighbouring tribes from raiding you, and their armies nail any external tribes who were raiding you. The empire is good. Internal rebellion then largely dies out - for sure you'll get ambitious people playing politics, but you're not up against continuous guerilla warfare.

This is a model which was somewhat followed by the British empire too. Often not very well of course (Amritsar, for example), but it was the ideal which apologists like Rudyard Kipling hoped to aim for.

So how do you keep the empire from falling apart? Like I said at the start, the reasons most empires died was because of bad succession management. That's what killed Rome, not the Visigoths. If you put a structure in place which ensures competence at the highest level, and which provides a well-defined way to continue that, then your empire can in principle keep going for as long as the people being ruled are still happy to be part of the empire.

In medieval Europe, there's only one institution which was capable of that, and that was the Catholic Church. Of course it was fundamentally corrupt, and religion had become a weapon. But as an organisation, it ensured the Pope was either a competent politician in his own right or a weak puppet who could be controlled by competent politicians behind the scenes. For an empire, either solution works. Feudal hierarchies of inheritance simply don't work for maintaining an empire, because (as all the European countries found) you only need one bad ruler to ruin things permanently. As a nice side effect of this, you can then use religion to tie your disparate puppet states together, which works very well.

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