Why the Bosphorus and not the Dardanelles?

[Velho e Bom Joe]

Tried a quick Google search, didn't turn up anything...
Basically, is there something special/better in the Bosphorus that does not apply to the Dardanelles? Why is Instanbul/Constantinople there and not on the Dardanelles? Pure chance/arbitrary picking by the ERE or was the land there outright better than other spots in the Dardanelles?

 

[Abdul Goatherd]

Tried a quick Google search, didn't turn up anything...
Basically, is there something special/better in the Bosphorus that does not apply to the Dardanelles? Why is Instanbul/Constantinople there and not on the Dardanelles? Pure chance/arbitrary picking by the ERE or was the land there outright better than other spots in the Dardanelles?

It seems more strategic. Dardanelles can be closed from both sides. Bosphorus can only be closed from one side. It gives you access to the Black Sea and is closer to Asia (trade and frontlines).

Although looking at chronology, Dardanelles was colonized first - indeed the first Greek overseas colony was Sestos on the Hellespont, colonized by Aeolians in the pre-Trojan War era. First towns on the Bosphorus itself were Chalcedon (east side, c.685), Chrysopolis (c.680, east side), Selymbria (west side, c.670) and Byzantion (west side, 659), all by Megarans, but this was after there were already Greek Ionian trading colonies inside the Black Sea (e.g. Sinope, Trabzon, c.750s) and colonies inside the Sea of Marmara (Cyzicus, c.750, Astacus/Nicomedia, c.711, Proconnesus, c.690).

 

[Emre Yigit]

The settlements on the Dardanelles and the Bosphorus are of very roughly similar age. I would guess the Golden Horn clinched the deal.

 

[Barsoom]

The Greeks settled both with a couple of cities. There isn't much difference between them in terms of size or importance. In the wars between Greeks and Persians the Hellespont was the most direct route for overland campaigns but it didn't lead to any city there gaining special status. (Well, unless you count Troy ca. 1200 BC.)

Differentiation begins with the Roman Empire. The Roman road system didn't connect Greece with western Asia Minor but rather the Danube frontier with Syria and the most direct route between those is across the Bosporus. When Diocletian instituted the tetrarchy, he chose a city near the Bosporus as the eastern capital, though not exactly on it but a little to the southeast on the Sea of Marmara and on the land route to Syria. Nicomedia was the eastern capital for nearly half a century, 286 to 330 AD.

Constantine selected the site for his new capital with 3 criteria:
1. The first is logistics, both in regard to the military highways and to grain imports from Egypt. Naturally this also facilitated trade. As the eastern half of the empire was richer than the western half, the city would profit from easier access to all this wealth.
2. The second is defense. A sufficiently big city would have water on three sides, thus needing strong fortifications only on one side. A successful siege needed both land and sea superiority. This only works for a very large city; the Greek forerunners were too small to benefit from it. Natural growth from Byzantion to Constantinople doesn't work like that, this was a planned city on a truly imperial scale.
2a. The biggest disadvantage of the site is access to fresh water, which was limited to a few springs and rainwater caught in cisterns. More water was brought in by aqueducts which could be cut by a besieging army. This was partly offset by more cisterns but in the 6th century a 56km long wall was built across the entire peninsula to try to protect more water sources, it had only limited success and was abandoned in the 7th century.
3. The third is symbolics. Constantine claimed that his new city had 7 hills like the old Rome and organized it similarly in 14 regions. Its status was initially a bit lower than Rome, for example its senators had only the title clarus instead of clarissimus, but it was definitely positioned as a remodeled imperial city and called Nova Roma. (It was renamed after Constantine after his death.) Ornaments were taken from cities and temples elsewhere so the city could be ready in short time.

As defense is only one of the criteria here, and since Nicomedia was already the center of the eastern empire without such natural defenses, it's unlikely that the Golden Horn alone clinched the deal. I think logistics is the key.

 

[Emre Yigit]

I had suggested the Golden Horn more as a harbour than a defence, though I suppose I should have made myself clearer. (And 17 centuries ago it was wider and deeper.)

Nicomedia does have a harbour (better than Constantinople's), but none of the places on the Dardanelles have anything remotely similar.

 

[diegosimeone]

Tried a quick Google search, didn't turn up anything...
Basically, is there something special/better in the Bosphorus that does not apply to the Dardanelles? Why is Instanbul/Constantinople there and not on the Dardanelles? Pure chance/arbitrary picking by the ERE or was the land there outright better than other spots in the Dardanelles?

The city of Byzantium that eventually became Constantinople was built in an area that was called 'Eptalophi'. Meaning, the 'Seven Hills'. Which was similar to Rome as well.

The English wiki is rather poor on the subject, but it's a good start.

Seven hills of Istanbul - Wikipedia

en.wikipedia.org

I see that @Barsoom made mention of this.

 

[diegosimeone]

In addition to this, you have to consider where they sit on the map.

The Dardanelles looks more strategic from a Black Sea perspective and a completely modern naval point of view.

But this was Rome, while shipping and trading was important, this was not just to become a trading center, but a very important city. So defense as others have stated was the key. And foot soldiers were very important.

Crossing the Dardanelles is harder than crossing from Anatolia towards Byzantium, not so much because it was a harsher gap, but because of the overall logistics to take an army to the city of Dardanelles or Abydos. Also, the narrow passage from Gallipoli towards mainland Hellas was never a friendly zone, so I suppose they had to improve that area significantly if it was to become a main center for the Romans and it did not offer that much of a strategic advantage, had marshes and was rather flat. And on top of that, they would still had to fortify the Bosphoros crossing at some point.


The Dardanelles also did not have that much space for a large port and it was also twice as long as Bosphoros. You had to fortify a strait from Gallipoli (Hellenic mainland) towards the Dardanelles (modern city of Canakkale and further south).

I'd say that the Dardanelles are far more important today than they were in the past, but they did ensure that naval attacks to the city of Byzantium were limited, assuming you control the passage. But still, the Dardanelles had to be controlled on both sides, but it was rather wide, apart from the point of the actual city of Dardanelles, so I'm not so sure if it could have been a very good naval defensive point rather than some sort of an outpost. It's not like they could fire cannonballs, all they could do was send out ships to block passage. If you chased a navy out of the Dardanelles, you ended up in the Aegean sea. On the other hand, in Bosphorus (or north of the Dardanelles to Gallipoli), you end up in the sea of Marmara, with the strait of the Dardanelles acting as an outer wall. Feels better for naval protection imo.

Not sure if in the case of having different governments controlling the two straits today if one would be more valuable than the other, but they both are extremely important if you're going to or coming from the Black Sea.

 

[Velho e Bom Joe]

Interesting. So it seems it was not one single, big advantage, but a bunch of small things (and historical events) that together gave the Bosphorus the advantage.

 

[GaiusC]

I'm not sure if this is sound strategy, I'm just wondering if this is another factor:
The Gallipoli peninsula is very thin, you can block it or control it with far fewer land tropps than you'd need to control the far thicker Byzantium peninsula. So if the capital was at Dardanelles, if you achieve naval superiority and land enough troops, you can cut the whole area, and this would cause massive supply shortages very fast. With Byzantium, you only need a short front to siege the city itself, but you need a massive amount of land troops to cover your rear front. Sure, the difference isn't as big as the one between the Thermopylae and Alesia, but still a big one.
So you can basically hurt a capital in the Dardanelles with far fewer land troops than Byzantium, which is bad for defense of the empire, and on the other hand there's no defensive advantage in case of a close urban siege, because you still have 3 sides of your city to cover with land walls. At the very least, if you were to pick the Dardanelles for your capital, you have to put it on the Asian side (Troy for instance).

 

[diegosimeone]

The city where the strait gets its name from is situated in Anatolia.

Its Turkish name is now Canakkale. By default, Dardanelles as capital would result in the capital being where Canakkale is today, ie the Asian side as you say.
As for the Troy remark, the Trojans were called Dardanians. The name Dardanelles itself is related to that and Troy was not far off.

The thin place you're talking about is Gallipoli, whereas the Dardanelles usually have Canakkale as their focal point, as it meets the first point of entry, whereas Gallipoli is closer to the Marmara sea.

 

[JodelDiplom]

The city where the strait gets its name from is situated in Anatolia.

Its Turkish name is now Canakkale. By default, Dardanelles as capital would result in the capital being where Canakkale is today, ie the Asian side as you say.
As for the Troy remark, the Trojans were called Dardanians. The name Dardanelles itself is related to that and Troy was not far off.

The thin place you're talking about is Gallipoli, whereas the Dardanelles usually have Canakkale as their focal point, as it meets the first point of entry, whereas Gallipoli is closer to the Marmara sea.

Canakkale (ancient Abydos) has a good location on the strait, but doesn't have the advantages that Constantinople has on land, though? It is not at the head of a peninsula, so its walls would have to be much longer given equal city size.

 

[diegosimeone]

Canakkale (ancient Abydos) has a good location on the strait, but doesn't have the advantages that Constantinople has on land, though? It is not at the head of a peninsula, so its walls would have to be much longer given equal city size.

Abydos is actually further up than Canakkale, right at the tip.
Canakkale was called "Dardanelles" and gave its name to the entire strait.


Cannot say how the landscape looked back then as it feels like an area where erosion could have shaped the land a lot over the last 500 years, but looking at the present map, it feels like Abydos could have been fortified using the tiny peninsula there. The city of Dardanelles, not so much.


I don't think the Romans could have picked a better spot than Byzantium honestly. You could argue Alexandria, Antioch, maybe Salonica or Halicarnassus or even an island like Rhodes if you wanted something around that region, but it feels like nothing beats the Chrysopolis/Byzantion area.

 

[Director]

There is a fairly strong current flowing north-to-south from the Black to the Mediterranean Sea. That means a fleet of Roman vintage would need favorable winds or have to do a lot of rowing, which multiplies the supplies you'd need to get a warfleet there with any speed. If you hold Byzantium you would logically fortify both Bosphorus and Dardanelles, keeping a fleet in the Sea of Marmara or - in extremity - in the Golden Horn or Black Sea. Byzantium can't be successfully besieged from the land alone - you have to have control of the seas to cut off supplies. When the Turks finally succeeded in taking the city they had to move ships overland - even with the diminished Byzantine navy, the Turks couldn't get past the city by water. Rowing upstream, you'd be open to a crushing attack coming downstream from ships secure in the Golden Horn or Black Sea.

The Gallipoli peninsula appears to have less usable land than the Byzantium site (meaning the whole Black-Sea-to-Marmara area), be hillier and have less fresh water. But I'm not familiar with the area and would like to hear from someone who is.

 

[Emre Yigit]

The currents in the Bosphorus are complex. You can move north if you hug either shore (preferably the eastern), but, yes, there is a strong central surface current moving from the Black Sea to the Marmara. I don't know about the Dardanelles, I'm afraid. I do know that prevailing winds are generally NOT from the north, though, which would mean there is no double whammy.

Spoiler: Off on a tangent

When the prevailing winds shift from the being from the west to being from the north (the "Poyraz" from the Greek "Boreas"), it changes the apparent colour of the Bosphorus strait from this

to this

due, I am told, to excess surface plankton being driven from the Black Sea.

I always thought the portage during the 1453 siege was due to the chain across the Golden Horn...

 

[Director]

Thank you for the information on the currents - I didn't know any of that, just that it was possible to float mines 'downstream' against the Allied fleet in WW1.

Yes, but the goal was to get control of the waters around Constantinople so that the city could be cut off from supply.

 

[Barsoom]

Thank you for the information on the currents - I didn't know any of that, just that it was possible to float mines 'downstream' against the Allied fleet in WW1.

Yes, but the goal was to get control of the waters around Constantinople so that the city could be cut off from supply.

There are basically 3 ways to win a siege. The first is through starvation, the second through force and the third through intimidation.

You don't need the Golden Horn to cut off supplies to Constantinople, Bosporus + Sea of Marmara is enough for that if you have the land forces to seal off both the western approaches and the land above the Golden Horn. A complicating factor was a nominally neutral Genoan colony on the north side of the Golden Horn, Pera, that could be used to smuggle supplies but Mehmed conquered it anyway so I don't think that was decisive. The problem was rather that starving out Constantinople could take a long time, especially since the city wasn't so densely inhabited anymore. Plus the Sea of Marmara blockade was broken at least twice, never by large enough fleets to carry significant supplies but first 4 and then 12 got past it.

The approach taken by Mehmed II was military force. He brought up cannons to breach the walls at a vulnerable place so the remains could be stormed. While he had the manpower to try at multiple places at once, the weakest section was the old walls in the northwest. Defeating the fleet in the Golden Horn took away their flank protection and added some pressure.

For intimidation you want to break the defenders' morale. This has been decisive in many sieges but in the case of Constantinople, which had very high symbolic value for most of its defenders, it was unlikely to be enough on its own; it would rather be a contributory factor for military force. You can of course reduce morale by starving the defenders and by showing military progress, so there is in case overlap with the other approaches. Mehmed started by taking the outlying fortresses one by one to show the defenders that the net was getting tighter. On the other hand, the arrival of ships through the blockade raised their morale. Taking the Golden Horn made this much harder, that's one part of it. Mehmed also executed captured sailors in view of the wall and left their corpses on display. The Genoese retreating from the walls when their general was wounded shows that morale was already weak when the final attack came.

 

[Yakman]

the harbor and the river.

pretty simple. hard to build a city of any size without water. hard to build a thassalocracy when you don't have a big harbor.