http://www.flickr.com/photos/mfspeccoll/4899716083/in/set-72157624742434942

This poster caught my attention because, while at first glance it appears almost like a religious motivational wall hanging (simple painted graphic, elegant text), the sentiment is actually quite warlike and vengeful.  Unlike in many of the other posters, it isn't about saving Belgian children or stopping starvation or upholding freedom--it's about getting a single headshot at a single soldier on the wrong side of the trenches.  It really brings home the perspective change from before to after the war.  The idea of honour and glory in war that was so widely subscribed to in those days played a major role in the sorts of propaganda that was produced, such that some such posters are actually jarring to read today.

What is really somewhat disturbing about this poster is the fact that it doesn't really matter what the cause is, who the enemy soldier is, or even how many the American soldier cuts down--only that he gets to kill at least one German.  His potential regret is not a failure to save someone, the loss of lives on his side or the others', or his level of courage.  Only the failure to kill.  Such ideas seem so deeply ingrained that I can't help but wonder if we ever would have come to our current understanding of war without having experienced it in such a painful way.