With all the factors/powers removed to have the Ottomans advance beyond Belgrade I really think this approaches ASB, but OK if it brings fun to someone at least...Hi Abdul
I'll have to comment on some of the things said though.
First, I think this very much underestimates the power of the Catholic Church and the Imperial idea. Even if the Habsburgs are for some reason taken out as players that doesn't mean anything else than another lucky family is given the chance (perhaps mine - Emperor Redbeard! OK, that has/had been done
). And the Turk landing in numbers in Italy really can't be overdone as rallying factor in the entire Christian world. If you'd like to call it a Saladin effect fell free.
If the Ottomans actually intend to supply their forces in Italy over the Mediterranean they're bloody hopeless in power projection of these centuries. Even when well stuffed magazines were available armies well into the 19th century were fed/supplied mainly by requisition/plunder (horse fodder making up roughly 2/3 of the total amount of supplies). It simply wasn't possible with the availabe transport to supply an army from magazines or from base. Operating in N. Italy would give rich opportunities for living off the land as long as you moved, but an Ottoman invading army would soon have to stop to lay siege and that's where the logistic problems seriously start. Even in rich N. Italy a besieging army would soon run out of supplies and from what I know of the Italian city states of the time much before the besieged. Here you have the main reason why war in N. Italy (and Europe until early 19th century) was so different from those experienced where the Ottomans usually hang around. I do not try to nullify the many good siege engineers the Ottomans had in these centuries, but I seriously doubt if they could storm the Italian city states faster than they could be relieved. I don't even think we need powers outside Italy, and anyway it is easier to feed in new armies from France than from Asia Minor, even if you have sea control.
And even if the Ottomans someway should nevertheless succeed. N.Italy then was such a concentration of wealth, culture, power and innovation, that it will soon be an open question who controls who.
All in all I think the Ottomans were lucky in OTL that they ceased so quickly to be a serious threat to central Europe, if they ever were. If they seriously step on the blue suede shoes they might be lucky if still holding Anatolia when the backlash is over.
Regards
Steffen Redbeard