What if: Frederick Barbarossa had seized Constantinople during the Third Crusade?

I've seen a lot of timelines and what-ifs describing a Byzantine resurgence at various points in their history. But what if the Byzantine Empire collapsed even earlier than in the OTL? Is it possible that a stronger and more stable alt-"Latin Empire" would have taken its place?

Unnecessary background: thanks to the disastrous leadership of Guy of Lusignan at the Horns of Hattin, the Kingdom of Jerusalem fell to Saladin in 1187. Possibly necessary background: the Byzantine Empire could care less about Jerusalem or Saladin, as their major focus was on Asia Minor and their primary rival was the Sultanate of Rum. Shortly after the fall of Jerusalem, the Byzantine Empire concluded a treaty with Saladin's nascent Abbuyid sultanate against the Turks.

Needless to say, this didn't go over well. Frederick Barbarossa sought and received permission to bring his armies across the Byzantine Empire by land, but once they arrived the reigning Emperor Issac II Angelos apparently changed his mind. Barbarossa ended up seizing the city of Philippopolis, and defeated a Byzantine army of 3,000 sent to relieve it. Eventually Issac II reconsidered and allowed Barbossa to pass through.

In the OTL, Barbarossa was apparently willing to let bygones be bygones, and led his Crusading forces against the Turks in Asia Minor. The Sultanate of Rum suffered several defeats, most notably at the Battle of Iconium where Barbarossa sacked and seized the Turkish capital city at Konya. The German Crusaders continued through Asia Minor, but Barbarossa died while crossing a river and the army dissipated before reaching its destination in the Holy Land.

But what if Frederick Barbarossa hadn't been so conciliatory with Issac II? The Byzantine Empire already had a strained relationship with western Europe, and had been recently weakened by war with Norman Sicily (which had sacked the city of Thessalonica). Issac II had secured his throne four years earlier with a victory at the Battle of Demetritzes, which drove the Normans off, but the Byzantine Empire was almost continually on the brink of disaster.

So what if Barbarossa hadn't agreed to help the Byzantines? What if he reconsidered and found that his position was a remarkably solid one -- with a larger army with many allies (notably including a Hungarian contingent) perched outside the capital city of a much-weakened empire? Barbarossa himself was the Holy Roman Emperor, and was famous for his political and administrative acumen as much as his military prowess. What could he have done, with the resources of the Byzantine Empire under his command?

I don't have the requisite knowledge to make a timeline of this on my own, but I consider it a truly fascinating divergence point in history that I'd love to see others continue. What could he have accomplished, and what would history look like had Frederick Barbarossa chosen differently?
 
A whole slew of specific factors allowed Constantinople to be taken by the Fourth Crusade. For one thing, the successful assault game from the Golden Horn. Does Barbarossa have a navy to be able to pull it off?
 
As RGB said, roughly.

Frederick simply doesn't have the logistics (his expedition may have depended too heavily on land roads) and ressources to undergo a full siege of Constantinople and a good part of imperial nobility he carried along may simply not agree with (and considering the focus given to counsel in military preparation in Middle-Ages, that's a problem) for both ideological and political reasons.
 
A whole slew of specific factors allowed Constantinople to be taken by the Fourth Crusade. For one thing, the successful assault game from the Golden Horn. Does Barbarossa have a navy to be able to pull it off?

I think he could've done with a navy, to be honest. Even a lifebuoy would've been an improvement, in the end.
 
I think he could've done with a navy, to be honest. Even a lifebuoy would've been an improvement, in the end.
If Fritz had a navy,he wouldn't be in Constantinople.He was there because he didn't have a navy and had to go from the land route.
 
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Not gonna happen. Constantinople was incredibly well fortified and defended, and Barbarossa's army wouldn't have stood a chance in taking it.
 
Thanks for all the replies! It seems the consensus among those who know better than I is pretty clear -- Barbarossa just didn't have the resources, particularly the navy, that he would have needed to make a siege successful.

So how about an alternative prompt? Specifically, where and how would Barbarossa have gotten the resources to enable the Third Crusade to seize Constantinople? What point(s) of departure -- in Western Europe and/or the Byzantine Empire -- would have given Barbarossa the same opportunity that the leaders of the Fourth Crusade had, to successfully besiege and seize the Queen of Cities, but at this earlier date?

Given the Hungarian contingent and that state's intermarriages with the Byzantines, I'm wondering if there was a Hungarian-born heir (someone low in the line of succession, but due to various deaths further up, realized that they have a halfway-decent claim) to give the Crusade the political cover t take the city.

Now to find Barbarossa a navy....somewhere....
 
To be frank,I just don't think it would be in Fritz's nature to attack Constantinople.The leaders of the crusaders were generally in it for four things:money,land,fame and good reputation with the Church.Given that Frederich has the former two,he is likely in it for the latter two.Given that he already rules a massive empire that's extremely difficult to govern,highly doubt he will try and expand his empire any time soon.I believe that the likeliness of odds of Fritz attacking Constantinople is the same as Hitler NOT attacking Russia in,ironically,Operation Barbarossa--which people will cry ASB in the post-1900 forum if you try and argue otherwise.

For the sake of argument,if he comes to the assumption that he needs to attack Constantinople,first he will need a good claimant.During this period,the only possible claimants would be Andronikos I's descendants.An even better claimant would be Alexios II if he somehow managed to flee Andronikos I.And no,no Hungarians have claims over the East Roman throne.There were Hungarian princesses that married into the East Roman Imperial family but not vice versa.Manuel I cancelled such a plan when he fathered Alexios II.I am entirely unsure why he would want to attack Constantinople at all if he's got a navy given it's a detour.However,if he doesn't have a navy and went the land route,with Isaac Angelos still trying to stop him from marching to Levant like OTL,AND Barbarossa actually backed someone with a powerful claim like Alexios II,then there's a chance that when he does attack Constantinople by land,Alexios' supporters and other opportunists might be persuaded to either open the gates to welcome back their legitimate emperor or launch an uprising to install Alexios II back as emperor just like how Justinian II did it.
 
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Specifically, where and how would Barbarossa have gotten the resources to enable the Third Crusade to seize Constantinople?

Seems hard to do. Not that Barbarossa didn't tought about fighting the Byzantines this from the start (see the Turkish embassy at Mainz's diet), that said, and probably intended to live on the land as he crossed the imperial borders.

First, Papacy would certainly frown a lot upon this, especially from the HREmperor (remember that 4th Crusade going rogue was already hard to swallow).
Gregorius VIII wasn't exactly the kind of man that will fall for such thing, being pretty much about saving the Latin presence in Holy Land. And without pontifical support, at least at first, it's hard to call such expedition a Crusade.

Then, he's not going to expect any real support from Richard I and Philippe II. The first was bound to gain renown, the other wasn't particularily thrilled by the whole thing and more ready to turn back in France to beat his ennemies while they would be busy elsewhere.

Going for a wild goose chase in a country they knew would cause issues (would it be only to supply their armies and cross the Bosphorus) for the benefit of Barbarossa was simply not about to motivate them.

Another point, that may look minor, is that the Fourth Crusade was successful because it was a nobiliar Crusade, and not an imperial one : basically we have a load of nobles full of tales of chivalry*, without much geopolitical impact to fear, and critically prone to reject (for cultural and proto-national reasons, as they were mostly from the Kingdom of France) the imperial suzerainty (critically after the failure of Henry VI to mount a successful Crusade in 1197**)

A certain bombastic and political attitude certainly supported the events, which may not be that much the case with an imperial/royal-driven Crusade.

* For exemple the Romans d'Eneas, which is an adaptation of the Aeneid

**Incidentally, how he used troops he gathered for a crusade to take on Sicily and possible plans to take on Rhomania may have greatly helped making 1204 Crusade more prone to attack Constantinople


To put it simply, if Barbarossa tried that from the start, he might find himself quite isolated, without much foreign or pontifical support, and possibly from his own troops.
As for navy, while not that needed to actually take on imperial navy (which was particularily reduced, due to imperial treasury issues and Isaac II incompetence), a very large part was already borrowed by Philippe and Richard, making use of Maritime Republic capacities unlikely for Barbarossa.

Don't get me wrong : he could have attempted that, it's not because we know it was implausible that Barbarossa and his followers knew.
But I don't see him being successful at this point : it would have been too son relatively to the Crusade's situation and imperial strength.
 
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