In my world, there was a huge empire spanning across several large continents. It was ruled primarily by a royal family with a number lower ranked governors to look after the individual states.

Looking back though, I realised this might not be that realistic. The Roman empire fell at its peak in around 500BC due to a large amount of reasons - one of them being that the empire was simply too large to sustain itself, the size making communication extremely difficult. The huge population was in constant demand for food and water, and there simply wasn't enough to sustain it. The size also made it difficult to keep the people under control. It was extremely difficult to march troops to defend the outer regions of the empire since it was so extensive. The empire I had was at least double the size of Rome.

To clarify - the empire lies inside a fantasy world. The heart of the empire is within a valley, with mountains surrounding the area on three sides. The civilisation spreads across about three land forms in total - one of them being a small chain of volcanic islands(similar to Indonesia or Hawaii), not far off from the other two continents. Although there aren't any modern communication methods, transportation or technology, this empire has a specific breed of small falcon-like birds who could fly around 150km/h for relatively long periods of time without breaks - generally used for communication, although sometimes horses and messengers are used. The road systems are not unlike Rome's, being quite efficient and can easily sustain the population. Chariots are the fastest method of transportation. The royal family, although not corrupt, are rather impulsive and inconsiderate, and are known for making decisions that affect the society greatly later on. There is a simple empress.

The empire is entirely self sustained - in fact, most of the inhabitants believe that they are the only civilisation in the entire world. (There are in fact others, but they are too far away.) The island chains are generally used as farmlands and livestock farms to sustain the population. Rivers run through the two larger continents - two, smaller rivers through the second continent - one eventually leading to a waterfall which cuts into the ocean - and two small rivers in the first continent, with one large one sustaining the heart of the empire.

This is my first question on here, so apologies if this isn't fully done to standard. Thank you!


closed as primarily opinion-based by Mołot, StephenG, sphennings, Azuaron, Josh King Feb 22 '18 at 15:11

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    $\begingroup$ Slight correction: The Roman Empire fell in 500 AD, not BC, and I think it was already well past its peak by that point. $\endgroup$ – F1Krazy Feb 22 '18 at 10:11
  • $\begingroup$ You should maybe consider asking instead of "how large can it get" - you will most likely only get qualitative answers that wouldn't help me if I was in your shoes tbo - stating what you want. Do you want it to collapse at a certain size, do you want it to work even though it is super large and want to know how to overcome some problems you don't know how to solve yourself or something else? Btw how can chariots be the fastest way of transportation, what gets faster when dragging a chariot? $\endgroup$ – Raditz_35 Feb 22 '18 at 10:11
  • $\begingroup$ Coruscant is a whole planet city that existed for thousands of years. And Rome you know Rome. It was there before Roman empire and is still there. $\endgroup$ – SZCZERZO KŁY Feb 22 '18 at 10:29
  • $\begingroup$ What about comunications? Is it possible to send messages with magic? And economy? $\endgroup$ – Sasha Feb 22 '18 at 10:56
  • $\begingroup$ While the comments have concentrated on mere technique -- communications & transportation -- in fact, it is social & political organization that are the important determinants of the survival of empires and their sizes.For long-term survival, China is a better model than Rome. $\endgroup$ – a4android Feb 22 '18 at 11:52


Empires do not have a set maximum size. If you look at the Roman Empire (or most other empires before colonial era, really) they expanded until something stopped them by making expansion in that direction non-profitable. Basically the limit is the ability to affordably transport armies for conquest or suppression of rebellions.

West had an ocean. East had the Persians. North was not friendly to available agricultural technology. South had the Sahara and beyond that. Additional factor was that compared to using ships on the Mediterranean anything else was expensive. After better ships and navigation were developed the economics changed and true global colonial empires happened.

In your case the travel between continents is by sea. If you assume that they conquered those continents, they must have ships and navigation good enough to travel between the continents with relative ease. This means they can keep their empire united. The holes in the empire will probably be in the continental interiors where some areas are too distant from the sea and navigable rivers to be worth supporting. But these will probably be covered by vassal kingdoms or areas with higher autonomy.

Basically, whether your empire is sustainable depends on how good your people are in sea travel. I'd go on the limb and say their navigation probably would be good enough. The two continents and major islands would supply incentive to develop better ships and navigation skills and it is not like building a ship that can do ocean travel requires very advanced technology by itself.


Not necessarily, this empire seems to be pretty stable as far as empires go.

One of the biggest reasons the Roman Empire fell was because their economy was geared towards constant expansion.

The British Empire only ended because of the world wars and the economic collapse that followed.

So, you need to ask yourself, what is the economy of the empire based on? And what are their capabilities for communication and projection of force?

If a colony on the fringes of the Empire is rebelling how fast the Capital can know about that? How fast can they deploy forces to suppress the rebellion?

How much power do local governors have to make their own policy?

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    $\begingroup$ An addendum to the British Empire (and other similar colonial empires): it didn't really "collapse" as much as it dissolved mostly voluntarily. Modern economy no longer favors huge areas of farmland inhabited by poor people, today every modern country has to pour money into such territories if it has them, instead of being able to make a profit from it. Also, the motivation and ideological views of the people changed: many European countries have the military strength to completely destroy their former colonies, but they lack the will (and their own population would revolt if they tried). $\endgroup$ – vsz Feb 22 '18 at 14:06

4500 km

If you are simply looking for evidence from the actual Earth, then the largest pre-modern empires that stayed intact for centuries had this diameter.

Empires that were large but did not stay intact for centuries include Alexander's conquests and the Mongol empire. Empires that did stay intact for centuries include Rome and China.

It is 4500 kilometers from Hadrian's wall in Britain to the Cataracts of the Nile. It is also 4500 km from Kashgar to the coast of the East Sea in what is now North Korea.

So from available evidence, the natural borders of expansion of an ancient empire seem to be limited at about that distance.


One limitation on how large an empire can go is how fast information can travel through it. How long until orders from the capital reach the outlying provinces? How long until taxes paid in the provinces reach the capital? If there is trouble, how fast can the capital respond?

You set your empire in a fantasy world. Is there magic that allows teleportation / fast travel / communication over distances? All of this would significantly stretch how big your empire can be.

  • $\begingroup$ Also a couple of dragons/tanks/nuclear weapons/anything bigger than anyone else has goes a long way to keeping the peasants in line. $\endgroup$ – Darren Bartrup-Cook Feb 22 '18 at 14:34
  • $\begingroup$ @DarrenBartrup-Cook : The peasants are usually not the ones who start a rebellion. It's a powerful group who wants to have more power, and uses the peasants to achieve that. Yes, their rule might (on rare occasions) benefit the peasants, but that is rarely if ever their main goal. $\endgroup$ – vsz Feb 22 '18 at 18:46
  • $\begingroup$ @vsz 'tis true. I was just using some kind of figure of speech I guess - blame the peasants, the peasants are revolting, clay peasant shooting (you should try that sometime, it's fun) .... $\endgroup$ – Darren Bartrup-Cook Feb 23 '18 at 8:56
  • $\begingroup$ @DarrenBartrup-Cook : What I meant was that a powerful group wants to usurp power from the empire, and use the peasants to achieve that. If they achieve independence, the peasants' life will often not become better at all, only the new leadership wins. This happened often in real life, after a territory gained independence it descended into warlordism, or the new government oppressed people even more than the old colonial power did. $\endgroup$ – vsz Feb 23 '18 at 13:46
  • $\begingroup$ @vsz And I was agreeing with you. An empire will collapse without the peasants to do all the menial tasks such as digging coal out of the ground. At the same time the peasants are quite happy to do that as long as they have the illusion of being slightly better off than before - they've been shown shiny things, or told they've slightly less chance of dying horrible under this dictatorship than the last. Of course it still happens today - slap how much we'll save on the side of a big red bus (truth doesn't matter) and enough of the peasants will go along with it. $\endgroup$ – Darren Bartrup-Cook Feb 23 '18 at 14:02

In every new country the Empire conquer has to be a loyal (to Emperor) leader and spy web to contro the country. If your empire has a single ruler, there must be a limit when he can't control amount of people that needed. And as soon as emperor stops controling sertain parts they can decide to rebel. Add couple of crises like earthquakes or whatever and you have a break in a system.


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