Ministry of Magic
In the fifth book, "Harry Potter and the Order of the Phoenix", the Ministry of Magic has been waging a smear campaign against Harry and Dumbledore, disputing their claims that Voldemort has returned. Harry is made to look like an attention-seeking liar, and Dumbledore a trouble-maker. A new character is introduced when the Ministry of Magic appoints Dolores Umbridge as the latest Hogwarts' Defence Against the Dark Arts instructor (and Ministry spy). Because the paranoid Ministry suspects that Dumbledore is building a wizard army to overthrow them, Umbridge refuses to teach students real defensive magic. She gradually gains more power, eventually ousting Dumbledore and seizing control of the school. As a result, Harry's increasingly angry and erratic behaviour nearly estranges him from Ron and Hermione.