The Second Blood War refers to a significant conflict in the fictional universe of Harry Potter, specifically involving the battle between the forces of Lord Voldemort and those opposing him, including the Order of the Phoenix. This war began in the late 1990s and was marked by a series of violent confrontations, leading to the return of Voldemort and his followers, known as the Death Eaters. The war culminated in the climactic battle at Hogwarts School of Witchcraft and Wizardry in 1998. Key figures in the conflict included Harry Potter, Hermione Granger, and Ron Weasley, who played crucial roles in the fight against Voldemort. The war ultimately ended with Voldemort's defeat, bringing an end to his reign of terror.