As I understand it, the Roman Empire was fuelled by expansion (stealing other people stuff), enabled by their exceptional military machine. Once they could not profitably expand any further, they were in trouble.

It lasted for many centuries after they ran out of stuff to conquer, so no.

The Roman Empire reached its maximum extent under Trajan around 117CE.

The decline began around 180CE to 235CE, depending on where you draw the line. That isn't 'many centuries' in my book.

Aren't you exaggerating it?

I lived in USSR, and know first hand that it means to be separated from common technological space. USSR wasn't that small, especially if one adds Eastern Block, yet it was falling behind the world becoming fully incapable to produce their own comparable computers, cars, etc.. If world get to split into such islands, the speed of technological progress will fall dramatically while social progress may go fully backwards. If you look at some ideologies rising around the world - they are straight medieval, and in many cases only connectedness to outside world has been preventing them from taking over their "islands".

Sorry, I probably should have quoted to which part I was referring. It's:

> with no technology to speak of for the 1000 years after Roman Empire

While it's true that some technology declined in the West, it wasn't as dramatic as you've suggested. Popular media also often exaggerates it.

https://www.britannica.com/technology/history-of-technology/...

Adding USSR into the discussion greatly increases complexity of the discussion. From analysis I've read, central planning is supposedly fine when country doesn't have much industry, because to start things up, it can provide essential investments and starts organizing production. But when country is somewhat developed, efficiency starts to matter and top-down approach to decision making of central planning vs bottom-up decision making mechanisms of markets produce different results. Politics and other things are important factors too, but I think that would be too much for this discussion.

As in -- "no technology to speak of" is a gross misrepresentation of the reality of the middle ages. The fact of the matter is, they were strictly more technologically advanced than the classical Romans, with inventions like the heavy plow and three-field rotation improving agricultural productivity significantly beyond what Romans had achieved.

> The fact of the matter is, they were strictly more technologically advanced than the classical Romans

No, they were more advanced in certain ways, but the original contention is correct that they were less advanced in others. Notably they were unable to build domes. They were also less productive, so less advanced in an overall sense.

What do you mean when you say they were unable to build domes?

https://en.wikipedia.org/wiki/History_of_medieval_Arabic_and...

Only the Western Roman Empire fell and even that part was fairly on track to recovery once Charlemagne came into the scene.

The fall of the Roman Empire is a pop history trope at this point.

Charlemagne empire wasn't an interconnected fabric of roads, trade, centralized administration and so forth, ie. it wasn't all that that Roman Empire was, and all that having gone is the fall of Roman Empire. Charlemagne empire was just an aggregation of conquered lands under his personal rule which thus he easily divided between his sons.

Yes, but my point was that a large state was created and managed centrally for quite a long time, and even the successor states were large.

More than that, technology continued to evolve. The Romans had nothing like Medieval plate armor, for example. There are many examples of better tech from the supposed "Dark Ages".

I think we are fine in term of infra -- I don't work as a civil engineer, but considering companies in my city repair the roads every year /s they probably retain the knowledge.

How easy is the machinery and tools needed to keep all the infrastructure running? Earth movers are pretty maintainable and barely depreciate. Survey tools though? They have gotten famcy right? Water management has gone quite high tech in some ways. I could see them falling apart kind of like when some hospitals had to revert to paper tape logs. It didn't scale anymore.

> Earth movers are pretty maintainable and barely depreciate

Beware hardware DRM locking up the repairs. That would make everything more fragile.

The infra today is internet and semiconductors which run it, as well as global shipping without each we end up without even necessities.

Exactly. Building roads and aqueducts were empire-level knowledge skills in Ancient Rome, performed by the army legions. Thankfully they're highly localized skills today.

Why stop there why not Indus Valley Civilization

our knowledge (at least my knowledge of it) is much much smaller that that of Roman Empire, and in particular i don't know whether the fall of that civilization demonstrated the effect of splitting into multitude technologically inferior pieces stagnating for such a long time after that.

_Washington Post_ just had an article about why (https://www.washingtonpost.com/opinions/2025/10/12/america-r...).

"In 1984, a German historian compiled 210 explanations historians had suggested for Rome’s fall, from lead poisoning and barbarian invasions to Christianity, moral decline and gout.

After studying dynamic civilizations such as Athens, Rome, Abbasid Baghdad, Song China, Renaissance Italy and the Dutch Republic, I can attest that there is no single explanation. Each golden age had its own character and its own downfall."

I always figured it was a combination of the volcanic winter of 536[1] and the Justinianic plague[2] (which happened right as the eastern roman empire was reconquering the western empire to reunify).

[1]: https://en.wikipedia.org/wiki/Volcanic_winter_of_536 and https://www.science.org/content/article/why-536-was-worst-ye...

[2]: https://en.wikipedia.org/wiki/Plague_of_Justinian

And i have my own ideas why it fell :) My point though ins't about pure why. It is about why it went into such feudal fractal mode.