In 1918, Woodrow Wilson's image as leader of the free world and the image of America as dispenser of democracy spread throughout Italy, filling an ideological void after the rout of Caporetto and diverting attention from a hapless ruling class. Wilson's popularity depended not only on the modernity of his democratic message, but also on a massive propaganda campaign he conducted across Italy, using as conduits the American Red Cross, the YMCA, and the Committee on Public Information.

American popularity, though, did not ensure mutual understanding. The Paris peace negotiations...