Mustafa kemal was the president of turkey that overthrew the last Ottoman sultan. There were different contentions and reforms that he enforced that were contrary to the Ottoman's modernity.
Kemal abolished the Ottoman Turkish alphabet and replaced it with Latin based alphabets.
He further introduced a new style of dressing for his service chiefs and government officials which was for them to wear western style business suits and abolished the use of the "fez".
The fez is a native hat that symbolized the Ottoman modernity which also a symbol of slavery. It was abolished completely as part of his reforms.