This poster is trying to get people who are living the happy life at home to help our soldiers who are fighting in the trenches
Uncle Sam wants more people to sign up for the army and fight for our country
this poster is trying to guilt you into joining the army by making you think that you are one of the only people absent from the army and that you should join
This poster is saying that if the cap fits then you join the army today. This is implying that everyone who can wear a cap and is able to fight needs to join the army.
This poster is getting people to join the army by saying that the U.S. needs you. Every single person that can join is needed.