Lord Arthur Ponsonby analyses mechanisms of war propaganda during WW I (1914-18): 'The Lie in War' [‘Falsehood in Wartime’ ] published in 1928,

1: We don't want war
2: The enemy bears all the responsibility.
3: We are not waging war against a people, but against an evil leader.
4: We are fighting for a noble cause, not for material interests.
5: The enemy commits atrocities.
6: The enemy is using weapons that are not permitted.
7: Our losses are limited, the enemy's losses are high.
8: The artists and intellectuals support our cause.
9: Every war is a 'holy war'.
10: Anyone who calls the propaganda into question is a traitor…

Facts must be distorted, relevant circumstances concealed, and a picture presented which by its crude colouring will persuade the ignorant people that their Government is blameless, their cause is righteous, and that the indisputable wickedness of the enemy has been proved beyond question. A moment's reflection would tell any reasonable person that such obvious bias cannot possibly represent the truth. But the moment's reflection is not allowed; lies are circulated with great rapidity. The unthinking mass accept them and by their excitement sway the rest. The amount of rubbish and humbug that pass under the name of patriotism in war-time in all countries is sufficient to make decent people blush when they are subsequently disillusioned.