Answer:
He believes O'Brien is an ally of the resistance, but finds that he is an ally of the government.
Explanation:
Winston is a member of a group that presents itself as a resistance to a tyrant, authoritarian, dictatorial and violent government. This group works for the liberation of the nation from this type of government, which is extremely harmful for all citizens and even for the future.
However, the resistance is strongly fought and tortured by the government, making it necessary for its members to protect themselves and remain hidden and in complete digil.
O'Brien finds out how to get in touch with the resistance and gives a speech that convinces Winston that he is an ally of the resistance and that he is committed to fighting the government. However, he eventually discovers that O'Brien is an ally of the government infiltrating the resistance to torture all those who are declared opponents of the government.
