The Brotherhood (Nineteen Eighty-Four)
The Brotherhood was supposedly founded by a man named Emmanuel Goldstein, one of the members of the original inner circle of the Party just below Big Brother himself. Like most leaders of the revolution, Goldstein turned on Big Brother but, unlike the others, he was somehow able to escape, and founded the Brotherhood. It remains unknown as to whether or not Goldstein exists and is still active, but if so, his location is unknown.
The Brotherhood cannot be said to be an "active" resistance movement, because its main goal is simply increasing in size slowly, in the hopes that generations in the future might pose a threat to the party. In order to build up to that day, the organization's purpose is to spread corruption by promoting prostitution, drug abuse, thoughtcrime, and other forms of criminal activities that would weaken the party in any way possible. In the film of the same name, O'Brien implies that perhaps in "A thousand years" there might be an attack on the party by The Brotherhood. However, in the present day, even if they are not active enough to actually cause any damage, the Party's propaganda blames virtually anything that goes wrong on sabotage by Brotherhood spies.
Supposedly, Brotherhood members do not even know one another. All Brotherhood members are expected to be captured, and when they are, they will not be rescued, as to protect the secrecy of the mysterious organization – most attempt suicide when captured if it is possible. As a result of their extreme likelihood of capture, Brotherhood members do not know more than 3–4 other members of the party, and if captured they consequently cannot betray any significant number of other members.
The Brotherhood's existence
Very little information is given as to whether the Brotherhood, or anything like it, actually exists in the novel. O'Brien heavily implies to Smith that all of the details of the Brotherhood and the very existence of Emmanuel Goldstein are just fabrications that the Party invented in order to lure out thought criminals and serve as a convenient scapegoat for the Party. O'Brien does allow that there might, hypothetically, be a real resistance movement similar to the fake Brotherhood, but if so, it has hidden itself so well that the Party has never detected it (the implication being, of course, that a movement so secret could never attain the level of organisation needed to genuinely threaten the regime).
The idea of the Brotherhood is, however, very real and is frequently used by the Party as a trap for potential thought criminals. Winston Smith, the novel's protagonist, is contacted discreetly by O'Brien. O'Brien pretends to be a member of the Brotherhood. However, he is really working for the Party, lying to gain Winston's trust and denounce him as a thought criminal. When Winston is captured and tortured inside the Ministry of Love, he asks O'Brien if the Brotherhood does exist. He tells Winston that that is a question he will never get an answer to, so it remains unknown as to whether it really exists or is merely an illusion created by the party.
The Brotherhood bears some resemblance to a real OGPU operation known as the Trust Operation, which was a fake anti-communist front group established to lure enemies of the Bolsheviks back from exile.