Why were posters like this one necessary to the U.S war effort?

During times of war, propaganda posters were necessary to rally public support, boost morale, and encourage participation in the war effort. These posters were used to convey important messages, such as promoting patriotism, encouraging conservation of resources, and recruiting individuals to join the military or support war-related industries. They were also used to demonize the enemy and create a sense of urgency and unity among the population. In this way, propaganda posters played a crucial role in shaping public opinion and mobilizing the country for war.