Synopsis
Before the Harry Potter series starts – when the character Lord Voldemort declared war on the wizarding world – Albus Dumbledore, headmaster of Hogwarts School of Witchcraft and Wizardry and a highly upstanding and powerful citizen of the wizarding world attempted to take control of the situation by founding the Order of the Phoenix. Several characters joined the organisation, seeking to prevent Voldemort from taking over the wizarding world and establishing a tyrannical new world order. During this period, before the events of the Harry Potter and the Philosopher's Stone, the Order sustained heavy losses, including the murders of minor characters such as the Prewetts, the Bones and the McKinnons. The Longbottoms were also tortured to insanity at the hands of Bellatrix Lestrange.
Voldemort's first reign of terror ended after the murders of James and Lily Potter, and the unsuccessful attempt to murder Harry James Potter at the beginning of the series. The spell rebounded on to him, and severely diminished Voldemort's powers and as a result the Order was temporarily disbanded due to the lack of any further threat.
When Harry Potter reported that Voldemort had returned towards the end of Harry Potter and the Goblet of Fire, Dumbledore reactivated the Order. Many of the original members returned and were soon joined by recruits who effectively replaced those who had died in service during the first conflict. The Order established their headquarters at Number Twelve, Grimmauld Place, Sirius Black's family home, during the interval between the fourth and fifth books in the series. Dumbledore was the Secret-Keeper for the Order, meaning that only he could reveal the location of the Order’s headquarters to others. Dumbledore's death at the hands of Severus Snape in book six made the location vulnerable and it was abandoned in favour of The Burrow as a result.
The Order led the fight against Voldemort in the fifth instalment during which the Minister of Magic refused to accept the return of Voldemort. In the fifth book, some Order members took turns guarding Sybill Trelawney's prophecy, which referred to Voldemort's downfall and Harry's role in defeating him. Rubeus Hagrid, the Hogwarts Grounds Keeper and an original Member of the Order, was accompanied by Olympe Maxime in an attempt to recruit the giants to the Order's cause. Some members also participated in a battle at the Department of Mysteries near the end of the fifth book. Order members patrolled Hogwarts, the Wizarding school, on the night of Dumbledore's death in Half-Blood Prince, fighting the Death Eaters who managed to enter the castle.
In the series finale, attention turned to escorting the Death Eaters' main target, Harry Potter, from his summer home with the Dursleys' to the Weasleys' Burrow. Later in the novel, after Voldemort's takeover of the Ministry had succeeded, some Order members hosted "Potterwatch", a secret pirate radio programme providing news on the Wizarding World that Voldemort's regime did not want the general population to know. During the climax of the book, most of the Order, aided by Dumbledore's Army, the Hogwarts staff and the older students, Slytherin house members excluded, fought against the Death Eaters in the Battle of Hogwarts, in which several Order members and other allies lost their lives.
As the Order was created primarily to combat Voldemort and his Death Eaters, it is unknown if the Order stayed together after Voldemort's death at the end of the story, or whether it disbanded as it had after Voldemort's first fall.
Read more about this topic: Order Of The Phoenix (fiction)