Final answer:
The propaganda poster depicting Uncle Sam with a raised fist and the phrase 'Avenge Pearl Harbor' is intended to spur action towards defeating Japan by either encouraging hard work in domestic industries or fostering military enlistment.
Step-by-step explanation:
Understanding World War II Propaganda
The question concerns a World War II propaganda poster featuring Uncle Sam and relating to the attack on Pearl Harbor. The message of the poster is to incite a desire for retaliation against Japan for the attacks on U.S. naval forces. The poster, reading "Avenge Pearl Harbor," seeks to do one of two things: either rally the American workforce to work hard at their job to aid in defeating Japan, or inspire individuals to join the military as a necessary step towards American victory over Japan. Considering the context of the Pearl Harbor attack and the subsequent emphasis on both domestic and military mobilization, the message of this particular poster is likely focused on encouraging enlistment to fight against Japan directly, hence, the message "joining the military is necessary for the United States to defeat Japan."