Kaiser Wilhelm II was the last German emperor and King of Prussia. As the leader of Germany in World War I, he represented the enemy nation. Negative words and images using "Kaiser," on posters and in parades, showed that Americans were supportive of efforts to defeat Germany. Some Americans questioned the loyalty of German immigrants or German Americans because of their shared heritage with Kaiser Wilhelm. 

The Kaiser had a very famous family tree, with complicated political connections during the war. His grandmother was Queen Victoria of Great Britain, so two of his first cousins included King George V of England, and Alexandra, who was married to Tsar Nicholas II of Russia. Kaiser Wilhelm also had direct family connections to neutral Spain and Allied countries Greece and Romania.