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Comment by Naga | Hacker News Reader

> Aqueducts were not a Roman invention, but in Roman hands, these long-distance aqueducts were developed further and extensively diffused throughout one of the largest empires in history

Roman water management is one of my interests (ask my wife, she will tell you that it's annoying how much I talk about aqueducts). The real invention though wasn't the aqueduct, although they definitely are engineering feats, since they require reasonably precise measurements and construction over long distances. The real innovation though was being able to maintain (relative) peace over their territory. Aqueducts are large and imposing, but also fragile and impossible to defend. Defending Rome's aqueducts required keeping the enemy out of Italy, for example. Rome's real success was over that part, not necessarily just the construction.

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I read that the aqueducts were a massive help for Constantinople during sieges. I always wondered why the attackers never destroyed the aqueducts, do you happen to know?

Great question. I am not too familiar with Constantinople's waterworks (I've been reading mostly about Rome itself). Off the top of my head, could be related to exactly where the aqueducts were built or placed. Parts may or may not be easily accessible, or underground in areas. Besiegers would also have to know they are there, since it wasn't as easy to google as it is now a days.

Quick search though shows that it had been cut during at least one siege: https://en.wikipedia.org/wiki/Siege_of_Constantinople_(626). The key is that you don't have to destroy the entire structure during a siege too, you just have to break ti enough that water doesn't flow through anymore.

Thanks that makes sense

If you plan to take the city, you have to break it without causing it to destroy itself. Water where it's not supposed to be can flood. It can undermine footings and destroy massive structures including itself.

If you want to destroy a fort you might throw a dead animal in the well. If you plant to keep the fort, that would be a titanically stupid idea.

You can cut off food supply and restore it the moment your flag is flying. Hell, you can stand the wagons on a hilltop as part of negotiating a surrender. How do you divert a river and put it back on demand, with not even medieval technology?

> How do you divert a river and put it back on demand, with not even medieval technology?

Now I am wondering how Kurus handled this situation after he took Babylon.

I wonder if that was actually a myth to hide the fact that he had inside collaboraters.

The priests of Marduk in Babylon hated Nabonidis due to his abandonment of Marduk worship and making another city his headquarters.

It may have been more acceptable to the population to tell them that the Persians diverted a river at night and entered rather than saying the gates were opened by insiders.

Floodplains are weird, for one thing.

On a small scale you can improve a stream by forcing the water to turn, using stones or posts driven into the water. If you have the ability to build a bridge, you have some ability to change the direction of the water.

In a floodplain or alluvial fan, all of the land is sediment from the river, which means that at flood stage the river has been everywhere and during a flood, or over geologic time periods, the banks of the river can shift. Oxbow lakes are old bends in the river that straightened themselves out.

In theory, if you had a city that was built beside the new banks of a river, you could go upstream and rechannel the river to an old course, either to expand the city or for nefarious purposes.

Also Babylon is, I think, a weird case anyway. If you look at a map of the Fertile Crescent, you see that the Euphrates forks, and it forks a LOT. And Babylon is located between two of the outer forks. Convincing a river that forks to chose another fork might just require some megalithic technology - throw some big rocks in until the flow rate slows rather than stops, and evaporation takes care of some of the rest. Or a phalanx of pilons all driven into the shadow of the next one up river (think geese in flight), which is how you divert a stream.

Even if the river doesn't stop, it might not have enough clear water in it to sustain a city under siege. Especially if you can get them to surrender before the next rainy season washes away all your hydraulic engineering.

Most enemies the Romans (they called themselves Romans through the final loss in 1453) that were strong enough to do threaten the aqueducts were on the other side of the straits. The Roman navy was strong enough to prevent large scale assaults on the European side. Occasional disruptions occurred, but when they became more than occasional was when the city really stared to weaken.

As they have always said, if you want to have good housing estates, there are three sound advices, location, location and location.

Personally I have been to Istanbul and the only main reasons I can think of Constantinople did not fall much earlier because of its strategic location at the edge of peninsular surrounded by natural three water/sea barriers and its extensive aqueduct systems.

Imagine the constant barrage of attacks from the Muslim Empires namely Umayyad, Abbasid and Ottoman over the course of around 700 years. This is due to prophecy that Constantinople will eventually fall to the Muslim army and only the best army General will prevail[1].

The attacks and sieges was started during by the Umayyad Empire in 674 and only in the year 1463 Sultan Fatih managed to finally subdue Constantinople for good. The only other time Constantinople was conquered happened during the Crusades'sacking in the year 1204. The Crusade invasion is only temporary and only lasted until 1261.

But the turning points of both of the successful sieges are very different. The Fatih's armies do not have direct access from the mainland and they do not have significant number of Christian Latin supporters in the Byzantine Empire and inside the fortress, unlike the Crusaders. The Ottoman basically have to resort to clever maneuvers like literally carrying the warships over hills to overcome the multiple chains barracades along the Golden Horn. The Ottoman was victorious probably due to conventional military strength and tactics but oblivious on the importance of aqueducts system supporting the lifeline of the city. The Crusades however, probably much aware of the importance aqueducts to the city due to their significant number of local Christian Latin supporters and managed to strangle Constantinople out of its lifeline. The recapture of Constantinople from the Crusade to reinstate the Byzantine Empire, however, is much easier because the Nicaean Empire obviously know the city inside out and the aqueduct systems.

This is my pure speculation based on my limited readings and observations of Istanbul, and more research needed to verify the potential causes of the fall of Constantinople and the importance of its aqueduct systems.

[1]https://www.dailysabah.com/feature/2015/05/29/the-conquest-o...

[2]https://en.m.wikipedia.org/wiki/Sack_of_Constantinople

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

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

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

Rome also was able to use its building prowess for military ends like few other powers.

Examples are Masada and Alesia. How do you assault a military fortress that sits on a shear cliff?

You either build a set a walls all the way around the city and starve it out (Alesia) or you build a giant ramp that is slopes gently enough to get your army and siege engines to the walls of the fortress(Masada).

Also the bridge of Apolonius was a major help in enabling Trajan to invade Dacia.

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