I'm thinking about the media campaign (that I obviously did not witness) that led up to the U.S. entering WWI. The American people were decidedly not enthused to enter a great-power struggle, and our large population of German immigrants and their descendents were especially opposed.
To swing public opinion, media campaigns began vilifying "The Hun," portraying German men with animal-like facial features and implying that we must go to war to prevent them raping French and English women and children.
Posters and newspaper articles from the time are very instructive. As are more personal recollections.
I once sat at my grandmother's kitchen table, reading through a box of her mother's letters, love letters to and from the US Army recruit who would later become her husband. They were both between 18 and 20 years old when the letters were written.
In one of them, he expresses his pain on being separated from his love, but says that he must do his duty to "stop the raping Hun."
Seems he heard the propaganda loud and clear and bought it.
The truth is that the US at the time had big problems with sexual violence, and US soldiers were a big part of the problem.
Army brass were aware of the problem, and employed measures like making sex workers more easily available to soldiers, I guess on the theory that they were raping women because they were deprived of sex and therefore just naturally had to rape. Sigh.
Nonetheless, propaganda against the "Hun" as a sexual threat to women and children continued.
A classic, time-tested method to justify slaughter and brutality!