Meaning of "The second step was to break the hold of Ottoman culture on Turkey itself."
It means to break the hold or reduce the influence of Ottoman culture on Turkey.
"The second step was to get rid of the Ottoman cultural influence over the nation of Turkey."
Break the hold of is being used metaphorically; for a literal use of the phrase, imagine a pair of wrestlers, Sam and Joe. Sam grabs the Joe's arm and holds onto it. Joe then twists in a particular way and breaks the hold, i.e. forces Sam to let go.