All history was a palimpsest

"If the Party could thrust its hand into the past and say this or that even, it never happened—that, surely, was more terrifying than mere torture and death." —pg 32

"Day by day and almost minute by minute the past was brought up to date. In this way every prediction made by the Party could be shown by documentary evidence to have been correct; nor was any item of news, or any expression of opinion, which conflicted with the needs of the moment, ever allowed to remain on record. All history was a palimpsest, scraped clean and reinscribed exactly as often as was necessary."

— Book One, Chapter 3

Who controls the past...

People simply disappeared, always during the night. Your name was removed from the registers, every record of everything you had ever done was wiped out, your one-time existence was denied and then forgotten. You were abolished, annhilated: vaporized was the usual word."
- George Orwell, 1984, Book 1, Chapter 1

"And if all others accepted the lie which the Party imposed—if all records told the same tale—then the lie passed into history and became truth. 'Who controls the past' ran the Party slogan, 'controls the future: who controls the present controls the past.'"
- George Orwell, 1984, Book 1, Chapter 3

"Day by day and almost minute by minute the past was brought up to date. In this way every prediction made by the Party could be shown by documentary evidence to have been correct; nor was any item of news, or any expression of opinion, which conflicted with the needs of the moment, ever allowed to remain on record. All history was a palimpsest, scraped clean and reinscribed exactly as often as was necessary."
- George Orwell, 1984, Book 1, Chapter 3