The Question and Answer section for 1984 is a great resource to ask questions, find answers, and discuss the novel.
The Party simply re-writes London's history to make BB look like the saviour of the city and the country.
This was during the great purges when the Party was taking over the government.
This is a pretty detailed question for this short space. Doublethink is essentially reality control. The power to hold two completely contradictory beliefs in one's mind simultaneously, and accept both of them. The above quote actually makes...