Pearl Harbor attack of December 7th, 1941
The Japanese planes bombarded the Pearl Harbor to keep the US from interfering with its expansion in Asia. This results the loss of many American battleships and soldiers. Thus, trigger a chance for US to join the World War II because people were angered from our territory being attacked even though we are neutral and was not part of the war.
A propaganda which fired up many people's spirit to go to war factories to work, to fight the war, to donate money, to contribute something. Reminding them the December 7th which the Japanese had secretly attack our Pacific naval base with air crafts.