With World War I an entire system of ideas how wars work collapsed. Suddenly it was no longer mostly soldiers who had to fight. War became an engagement of every day's life. Everybody got involved.
Propaganda therefore changed as well. The campaigns were no longer temporarily and recent but had to be planned for years. Who failed in organizing it or used the wrong keywords failed. Masters of modern propaganda became the British, whereas the Germans failed completely in the beginning.
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Though Sergei Eisenstein (1898-1948) made only seven films in his entire career, he was the USSR's most important movie-conductor in the 1920s and 1930s. His typical style, putting mountains of metaphors and symbols into his films, is called the "intellectual montage" and was not always understood or even liked by the audience. Still, he succeeded in mixing ideological and abstract ideas with real stories. His most famous work was The Battleship Potemkin (1923).