In Part 2 of the novel, How does McMurphy signal his return to battle with Nurse Ratched? Why does he decide to fight?

I believe that he rips her dress open and acts as though he is going to stangle her. She has him taken for a labotamony and when he returns he is not the same. After that nurse racheat loses all power over the patients and they either transfer or check themselves out of the hospital.This fight has become part of his own search for identity, even sanity.