Dolores Umbridge is appointed as the Defense Against the Dark Arts teacher and later becomes Hogwarts’ High Inquisitor. Under her dictatorial leadership, the Ministry of Magic imposes strict control over the school, forbidding practical defense lessons and punishing dissent. Despite increasing signs of Lord Voldemort’s return, the Ministry refuses to acknowledge this threat.
In response, a group of students led by Harry Potter forms Dumbledore’s Army (D.A.), a secret organization that teaches practical defense skills, promotes student solidarity, and prepares for the dark forces ahead. Participation is explicitly against school rules and, if discovered, could lead to expulsion or other serious punishment.