I understand HOW: I do not understand WHY - George Orwell

The essential job is to get people to recognise war propaganda when they see it, especially when it is disguised as peace propaganda.

He wondered vaguely whether in the abolished past it had been a normal experience to lie in bed like this, in the cool of a summer evening, a man and a woman with no clothes on, making love when they chose, talking of what they chose, not feeling any compulsion to get up, simply lying there and listening to peaceful sounds outside. Surely there could never have been a time when that seemed ordinary?

And yet, just for a moment, what almost frightening power had sounded in that cry from only a few hundred throats! Why was it that they could never shout like that about anything that mattered?