It is a somewhat little-known fact that, after the Fall of Constantinople, the Ottoman Sultan Mehmed "the Conqueror" was given the title "Caesar of Rome" (Turkish: Kaiser-i-Rum), considering himself and the Ottoman Empire to be the successor to the Roman (and Byzantine) Empire, based on his capture of Constantinople ("New Rome").
This title was ignored by the majority of Christian Europe, even the Patriarch of Constantinople. Eventually, this title was forgotten, and the successors to the Sultan preferred the titles "Sultan of the Empire" and the "Caliph of Islam" instead. The dream of succeeding the ancient Roman Empire ended.
But what if, by stroke of luck, the Sultan was able to get the title he long dreamed for, even for a short while? What would become of the world with an Ottoman Caesar of Rome?
In this timeline, during the Battle of Torvioll, the League of Lezhë's leader, Skanderbeg, is fatally shot. The League collapses, and the Ottoman Empire expands into the Albanian territory to ensure their sovereignty.
Fast forward, after the infamous Fall of Constantinople. The Venetians and Ottomans get into conflict in 1463, with many in Europe wanting to take the Ottoman influence out of Europe. But without the Albanian rebels plight for freedom, the war with Venice ends years sooner, and neither nation had to waste years or resources.
Less than a month after the peace, Mehmed has a dream of capturing "Old Rome," believing it to the the will of God. With a less-extensive war with the Venetians, the Sultan could prepare his army and his growing navy for the biggest challenge of his life.
By 1470, Mehmed has prepared all of his army and navy to attack the Italian peninsula. The Ottomans and Christian Europe take part in an almost five-decade long war over the Italian peninsula, one that results in the sack of Rome, in what many say is "short of a miracle" and "a feat that not even Pyrrhus of Epirus could manage". Mehmed would pillage the city, and soon establishes a Patriarch in the war-torn holy city that was Rome. He converts St. Peter's Basilica into a mosque, flies his flag victoriously over the city, and establishes his rule over the ancient city. Mehmed finally gains the recognition he so long desired as the Caesar of Rome.
Alas, the victory could not last for too long. Europe would not bear to watch as the very centre of the Christian world is taken by the hands of the "evil Mohammedans." After decades of bloodshed and violence, the Turks are driven right out of the peninsula and back from whence they came. Mehmed does not live long enough to see the title ripped away from him, but his legacy outlives his title, as the world would never be the same...