There were somewhere on the order of a dozen crusades called for over the course of the 1400s, but most went unanswered, and the few that came to anything came up just a bit short, often to the point of bad luck. In my opinion, any time before Mehmed II takes Constantinople the Ottomans are in serious danger of falling apart. They are an empire without a significant navy divided in two by a semi hostile bosporus and the Venetian vulture looking for anything that they can profit from. Worse still, approximately half of their people if not more are still Christian and definitely not Turkish. Mehmed II fixes the most important problem by taking Constantinople, adding more Islamic turkish subjects through his eastern conquests, and creating the beginnings of the Ottoman navy as a dominant force. He also did a good job of milking the idea that he was better for Orthodoxy than the Pope by naming his own patriarch of Constantinople and keeping him in his pocket. Without all of this, the Ottoman Empire is still quite fragile in my opinion, and a significant defeat by westen forces that is actually followed up on could very possibly cost them their lands in Europe.
I'm not sure, depends on Timur.
OTL they tried. Timur did wonders to cool their enthusiasm about it rather quickly.
His bloodthirstiness had something to do with it, I think.
I'm not sure, depends on Timur.
During the Ottoman Interregum the House of Osman was split between four sons fighting for control and dominance. Through this period the main divisions of the Ottoman lands had a fairly consistent Rumelia/Balkans and Anatolia split. It also had the Byzantines, Serbs, and other Beyliks joining the fight supporting sons of Bayezid (who was killed fighting Timur).
At one point, the son Musa after being defeated and bidding his time successfully launches a coup that kills his brother Sulemayn on the Rumelia side. Showing anger at the Byzantines for supporting his brother, Musa attacks Constantinople which leads Manuel to throw his support behind Mehmet on the Anatolia side an help him bring over an army and kill Musa (in a battle which almost went in Musa's favor I might add).
What if instead Musa allies with the Byzantines, but instead of finding victory over each other their fighting (influenced by the Byzantines) fails to conclude in a desisive victory. Leading to two seperate political entities to grow apart. Importantly I am interested in any sort of cultural changes such as one of the two becoming more Islamic or more European or etc.
Basically, I want to see if two Turkish states could emerge and not be wiped out or merge. This might lead to a greater Islamization of the Balkans population or even no Vienna invasion or even the Byzantines surviving longer if they can play off the two sides.
That was how the Ottomans started the tradition of pitting sons against each other for the throne, right?
But wasn't there a time when the Ottomans put a stop to that kind of practice?
Anatolia is definitely lost, but the Byzantine Empire could at least hold on to Greece, southern Bulgaria and a couple of islands. Another thing I need to figure out is which Balkan power other than the Byzantines or Hungary would be suitable to maintain the balance of power? Could we have another Turkic power besides the Ottomans coming to power in Anatolia though? Either the White Sheep or the Black Sheep Turks. Heck, why not have the Safavid tribe shift westwards? For all we know, we haven't seen a TL where Anatolia becomes a Shia dominated territory.
Karamanids? They did exist even when the Ottomans rose to power. A Karamanid Empire would actually be interesting, and they'd only focus on the Middle East. Leaving the Balkans free from Ottoman incursions, though it would be a contested ground between Bulgaria, Hungary, the Byzantine Empire and Serbia. As to how can the Karamanids conquer the Ottoman Empire and possibly expand elsewhere?