Orwell, George — Nineteen eighty-four [727]

A mighty deed, which could never be mentioned, had been achieved. It was now impossible for any human being to prove by documentary evidence that the war with Eurasia had ever happened. — Orwell, George, Nineteen eighty-four, 727

Note

The oxymoron of an unmentionable ‘mighty deed’ — an achievement that erases its own record — captures the whole premise of historical rewriting in two sentences.