So the Ottoman Empire takes control of Vienna, what'll happen as a result? What is Suleiman's next plan of action?
Wouldn't the rest of christian Europe panic should the turks expand further into Christendom? Both Protestants or Catholics would see the danger of the expansion of Islam. Also should the Ottomans make a play for Italy they'd face French power as well.
Is Suleiman is smart, he'll mostly go on the defensive after Vienna, and concentrate on tightening his grip on Hungary by eliminating the remnant still in Habsburg hands. There's little mileage in trying to go further.
IIRC, Ottomans didn't even take over central Hungary until 1541 OTL, so ITTL they'd need to annex Hungary beforehand, which probably would make them unable to reach Vienna 1529, as they'd be busy establishinh direct control of Pannonian Plain.
It would've been easier indeed had Hungarian king not died in Mohacs. Annexation wasn't what the Ottomans originally had planned for Hungary, after all.
What were the Ottoman aims regarding Hungary, before Mohacs?
Defeating a military threat and establishing a defined stable frontier. Perhaps vassalage or a "Finlandization"of Hungary (under a surviving king).
I think that given logistics taking Vienna is possible - holding is not.
And BTW Vienna is not the direct path to Venice and Rome - controll of todays Slovenia/Croatia would be sufficient...
In addition the HAbsburg center of this day was not "Austria" but Spain, so the loss of Vienna (which was exposed at the border of Habsburgs lands is maybe not the blow it would have been in 1683.
I'm not sure if the logistics argument is that clear cut - after all, in 1532 Suleiman was leading a larger army, across harsher and further terrain and against an enemy that had resorted to scorched-earth tactics to stop him, and yet he still managed to capture a lot of what is now Kurdistan, Iraq and Western Iran from Persia. Much better weather than OTL and more luck in Ottoman mining operations and it's not unreasonable to expect the Ottomans to be able to capture Vienna in time to fortify it against any inevitable reprisals, as well as open the Danube (which was navigable by the Ottoman fleet) as a permanent logistics corridor of sorts. Buda, after all, was a key Ottoman base during OTL.
Yes on a map Vienna is not a direct path to Venice and Rome, but if we assume the Ottomans march along the paths of the old Roman road and also have to avoid Venice-controlled Dalmatia, they would have to move north from Belgrade, skirting the Hungarian plain before entering Slovenia, which would leave their logistics/communications open to an Austrian force moving down the Danube. So capturing Vienna would secure a major road/riverway facilitating that.
Sure the Habsburgs won't roll over and die if Vienna is annexed. Ottoman plans for taking Rome or Venice might not succeed either, and I would definitely agree that logistics is a serious issue there. Doesn't mean the Ottomans won't try to do it. I would think the psychological allure of 'key objectives' - from Rome to Constantinople to Moscow - has a tendency to overpower any logical assessments of the situation.
In addition the HAbsburg center of this day was not "Austria" but Spain, so the loss of Vienna (which was exposed at the border of Habsburgs lands is maybe not the blow it would have been in 1683.