I’m the book 1984, How does O’Brien Interrogate Winston?

O'Brien forcefully questions Winston and wants him to truly understand and believe that the only truth is what the Party says is true. O’Brien uses passive aggressive techniques over Winston's body and psyche. Whenever Winston falls short of his intellect, O'Brien inflicts pain on Winston. At times O'Brien holds Winston like his saviour and at others , O'Brien is a torturer sending waves of excruciating pain through Winston's body. The dichotomy of both saviour and torturer being one and the same emerges in the latter part of the story. In the end, O'Brien "cures" Winston of his mental fallacies by cauterizing who he used to be.