Propaganda was heavily utilized in both world wars. While it was used to galvanize patriotism, inspire people to enlist and buy war bonds, and vilify the enemy in both instances, there were differences that developed from one conflict to the next.
For one thing, the propaganda of WWII was much more racialized than it was during WWI. Nazi propaganda painted Jews and Slavs as sub-human beings who were bent on the destruction of Aryan civilization. Japanese propaganda portrayed Americans as savage, uncivilized beasts. In turn, American propaganda depicted the Japanese as mindless and destructive animals. By dehumanizing the enemy, WWII propaganda allowed many to rationalize atrocities on a level that the world had never previously experienced.
Another change that set WWII propaganda apart from that of WWI had to do with technological advancements in the media. During WWI, cinema was still in its infancy. There were some silent films used for propaganda purposes at that time. However, by WWII, cinema had developed into a fully-realized art form and propagandists were eager to utilize it. In America, regular programs such as "Why We Fight" aired in theaters to justify the country's involvement in the war. Other movies promoting patriotism were produced at a fast pace. The Nazis were also keen on developing their own distinct cinematic style for the purpose of promoting their agenda. Leni Riefenstahl, a German movie director, created dozens of propaganda films promoting the Nazi cause. In doing so, she revolutionized cinematic techniques, many of which are still used today. Animation also developed by the time of WWII. Cartoons for children and adults readily promoted the war effort.