In 1984, the Brotherhood is the name of the secret organization whose role is to bring down the Party. In Part Two, Chapter Eight, when Winston and Julia are at O'Brien's apartment, the reader gets a sense of how the Brotherhood fulfills this role. Its members murder, cheat, forge, and betray their country. In order to keep its membership and activities secret, the Brotherhood keeps no records or membership lists.

In Part Three of 1984, however, it becomes clear that the Brotherhood (and its head, Emmanuel Goldstein) do not exist. This has an important effect on the Brotherhood's role: instead of being a protest group, the Brotherhood is used by the Party to highlight those who secretly wish to rebel. Once the Party knows the identities of these people, it imprisons and tortures them until they relent, as we see in the cases of Winston and Julia.

In George Orwell’s classic story of a totalitarian society in which Big Brother monitors every citizen for signs of nonconformity, the existence of “the Brotherhood” is something of a mystery.  Through much of 1984, the reader is uncertain whether this resistance movement allegedly led by a former high-level regime official, Emmanuel Goldstein, actually exists, or whether it is a myth, possibly created by the government to justify its repressive measures.  Early indications of the mystery surrounding the Brotherhood’s existence are provided in passages like these in which, in the first two examples, Winston contemplates the rumors surrounding Goldstein and his movement and, in the third, Winston describes Julia, whose affair at the age of 16 with a Party member aged 60 threatens her existence:

“He [Goldstein] was the commander of a vast shadowy army, an underground network of conspirators dedicated to the overthrow of the State. The Brotherhood, its name was supposed to be."

“Perhaps the rumours of vast underground conspiracies were true after all—perhaps the Brotherhood really existed!”

 “She had never heard of the Brotherhood, and refused to believe in its existence. Any kind of organized revolt against the Party, which was bound to be a failure, struck her as stupid.”

As 1984 progresses, whether the Brotherhood actually exists remains a matter of speculation.  Its size and the level of threat it may pose to the regime is considered extremely limited, as suggested in this passage from Chapter 7:

“Even if the legendary Brotherhood existed, as just possibly it might, it was inconceivable that its members could ever assemble in larger numbers than twos and threes.”

The mystery surrounding the existence of the Brotherhood provides one of the novel’s most complicated elements.  1984’s main antagonist, O’Brien, discusses it as a real movement, such as when he tells Winston, “I tell you that the Brotherhood exists, but I cannot tell you whether it numbers a hundred members or ten million,” and, as the two discuss it in the following exchange:

"‘Then there is such a person as Goldstein?’ he [Winston] said.

‘Yes, there is such a person, and he is alive. Where, I do not know.’

‘And the conspiracy—the organization? Is it real? It is not simply an invention of the Thought Police?’

‘No, it is real. The Brotherhood, we call it. You will never learn much more about the Brotherhood than that it exists and that you belong to it.”

O’Brien seemingly confirms the existence of the Brotherhood, but Orwell cleverly allows for the possibility that it is a creation of Big Brother, intended to draw out of the population potential rebels seeking to join the resistance movement.  A real-life parallel existed, to which Orwell was almost certainly knowledgeable: following the Bolshevik Revolution in Russia, the new regime’s intelligence service, known as the Cheka, established a phony organization in Europe called “the Trust.”  The Trust posed as an anti-Bolshevik political movement that attracted Russian emigres hostile to the communists.  Once approached by unsuspecting dissidents, the Cheka moved in for the kill.  1984 was Orwell’s answer to the Soviet Union’s repressive, autocratic regime.  The Brotherhood might well have been his version of the Trust.

The Brotherhood is the secret, anti-government organization headed by Emmanuel Goldstein. Whether or not the organization really exists is not made 100% clear, but it is doubtful that it exists. More likely, it, as well as Goldstein, are made up by the government of Oceania as a means of seeking out revolutionaries and anarchists. Also, by letting people believe that this person and organization exists and then by showing people the terrible fate that befalls those who join or associate with this organization, the Party keeps people in line. People see or hear about the tortures carried out against anyone who tries to go against the Party and their fear of that happening to them keeps them from going against the Party. In the story, Winston tries to join the Brotherhood and that is how O'Brien traps Winston and Julia who eventually are tortured into loving Big Brother and the Party. Essentially then, the Brotherhood is merely bait dangled by the Party to catch those who might want to overthrow the government.