
God, sometimes I wonder if Ataturk is treated in Turkey the same was Roosevelt is treated in the states, or Churchill is treated in Britain.
Think more like George Washington + Luke Skywalker + Jesus.
Anyways, I don't think it would change THAT much- it depends on the specifics of his role at Gallipoli. He was in command of one of the local reserve regiments which IIRC, made it pretty certain that the allies never made it off the beaches. That being said, the whole campaign was so buggered from the UK end, and the Ottomans knew it was a fight-or-die battle, so I don't really see Gallipoli working just because Mustafa Kemal Pasha isn't around.
The real changes, of course, happen post war. This is where it gets tricky to separate man from myth. Militarily, things aren't really that different. Turkish (and I mean ethnic Turkish) resistance still starts when the French send in ethnic Armenian colonial troops, and when Greece moves into Izmir. Izmet Inonu still fights at.....Inonu (aah, postwar last name choices) and the last intact Ottoman army will still be under Kazim Karabekir in the east. The Grand National Assembly (TBMM) probably will still convene in Ankara, and the Greeks will probably be defeated- although exactly how and how easily will be affected by butterflies somewhat.
The big change is that, while there was a pool of nationalist, competent army officers who wouldn't accept foreign occupation, Ataturk was the "vision guy"- for better or worse he railroaded his vision of secular nationalism through the assembly. It's worthy to remember that the first session of the TBMM was preceded by Koran recitations, processions to local Sufi shrines, and was ostensibly convened in the name of the Sultan in order to save him from his imprisonment under foreign occupation.
Things would get
very interesting once the nationalists muddle through a few military victories on that line.