Best POD for Successful Crusade of Varna?

[Behemoth]

The fortress was situated at the narrowest point of the Bosphorus, IIRC, and was designed to withstand attacks by catapults and similar siege engines. The one advantage that the Europeans have is that Rumelihisari was not built until 1451. With both fortresses in place on either side of the straits, it would be quite effective at controlling the flow of ships in between the Black Sea and the Aegean.

In regard to artillery, I am not sure if Hunyadi would have been able to attain cannon outside of Hungary. The Ottomans in OTL had acquired quite a large amount of materials and manpower to not only help construct Rumelihisari and to conduct the siege but to make the cannons as well. I have not found much on the iron founder and engineer, Orban, prior to the siege. He was supposedly either Hungarian or German and did offer his services to the Byzantine emperor in 1452. The emperor, unfortunately, could not afford to pay his salary or provide the necessary materials to construct the cannons.

There are some problems however:
- payment of services to the engineer (Orban is possible since he may have been working in 1444)
- attaining the necessary resources needed to construct the cannon
- transport of the cannon
- maintenance

I am not sure of the state of finances of the Hungarians at the time but the services needed as well as the resources needed would cost quite a large sum. If, for some reason, the money is procured, then there are further issues with its use. Transporting the cannon(s) would take time and manpower for them to be used. Carts would require more materials, cannonballs would need to be made, and gunpowder would need to be stored. Also, if not careful, there is a possibility that the cannon can develop cracks and/or explode during battle.

In regard to what kind of artillery would be needed for an attack on Anadoluhisari, I am not sure and I have not found figures in regard to the structure prior to 1453.

 

[Achaemenid Rome]

The fortress was situated at the narrowest point of the Bosphorus, IIRC, and was designed to withstand attacks by catapults and similar siege engines. The one advantage that the Europeans have is that Rumelihisari was not built until 1451. With both fortresses in place on either side of the straits, it would be quite effective at controlling the flow of ships in between the Black Sea and the Aegean.

In regard to artillery, I am not sure if Hunyadi would have been able to attain cannon outside of Hungary. The Ottomans in OTL had acquired quite a large amount of materials and manpower to not only help construct Rumelihisari and to conduct the siege but to make the cannons as well. I have not found much on the iron founder and engineer, Orban, prior to the siege. He was supposedly either Hungarian or German and did offer his services to the Byzantine emperor in 1452. The emperor, unfortunately, could not afford to pay his salary or provide the necessary materials to construct the cannons.

There are some problems however:
- payment of services to the engineer (Orban is possible since he may have been working in 1444)
- attaining the necessary resources needed to construct the cannon
- transport of the cannon
- maintenance

I am not sure of the state of finances of the Hungarians at the time but the services needed as well as the resources needed would cost quite a large sum. If, for some reason, the money is procured, then there are further issues with its use. Transporting the cannon(s) would take time and manpower for them to be used. Carts would require more materials, cannonballs would need to be made, and gunpowder would need to be stored. Also, if not careful, there is a possibility that the cannon can develop cracks and/or explode during battle.

In regard to what kind of artillery would be needed for an attack on Anadoluhisari, I am not sure and I have not found figures in regard to the structure prior to 1453.

Oh, I didn't realize that only Anadoluhisari was in existence at that time.

Since Rumelihisari hadn't been built yet, and Edirne was reasonably far inland, it seems Hunyadi might not need the bombard at all. He could just surround the city of Edirne and besiege it the classic way by preventing the city from being reinforced with troops/supplies. The Byzantines sending Orhan Celebi to wreak havoc in Anatolia, and the Karamanid invasion, would distract Ottoman attempts at reconquest.

The Turks built the Dardanelles gun at Edirne, so once Hunyadi takes the city, he could theoretically build one there as well. However, if the goal of pushing the Ottomans out of Europe is successful, the Crusaders could negotiate peace before crossing into Asia, so they never need to attack Anadoluhisari.

Anadoluhisari does makes it more dangerous to cross through the Bosporus into the Black Sea (to reinforce Varna for example), but the Genoese did manage to hold their Black Sea colonies for two decades after the fall of Constantinople, so they could potentially make it through.

There is the issue of Varna, which the Ottomans might be able to sail to and then reinforce. Though it appears Hunyadi and Ladislaus were able to take/enter the port of Varna without much difficulty, before the pivotal battle outside of the city.

 

[Monter]

I am not sure of the state of finances of the Hungarians at the time but the services needed as well as the resources needed would cost quite a large sum

Badly, I don't have my book here, but the figures about the treasury of the Hungarian crown in 1453 was around 150,000 florins yearly, also Hungary was in the middle of a civil war with the Habsburgs, so they aren't in the best pockets.

 

[Fehérvári]

The latest and most plausible POD for a succesful crusade of Varna is 30 minute prior to the end of the Battle of Varna. Make Vladislaus listen to Hunyadi's advise to not do anything stupid and sit tight until the battle is won.
With this POD Hunyadi defeats the Ottoman army and wins the crusade. Bulgaria most probably is liberated in the process. Serbia gets punished for its treason. Other succesful crusades in the future against the Ottomans might occur, resulting in a Hungary dominated Balkans. Constantinople never falls.

 

[Jan Olbracht]

Lates POD would be propably good enough to prevent catastrophe, but not for really successful crusade. Ottomans had vas numerical advantage. IMHO POD with Murad's death in Sofia is the best.
King Władysław was easy to manipulate (he was manipulated by bishop Oleśnicki in Poland and then by Cesarini in Hungary) and likely to get crusade fever after such success. His position definitely would improve-IOTL he made compromise with Habsburgs-he promised to abdicate Hungarian throne once Ladislaus the Posthumous reached adulthood. Now no one would demand him to fulfill his promises.