![](https://paw.princeton.edu/sites/default/files/styles/feature_image/public/images/content/FTA030619new.jpg?itok=pvxF2uFS)
In the spring of 1917, Princetonians mobilized for World War I after the United States joined the Allies to fight the “war to end all wars.” Army, Navy, and Army Air Service training schools were set up on campus. In this photo, officer candidates practice tapping out Morse code in the basement of the Palmer Physical Laboratory.