President Gregory d'Allessio, of the Arts Student’s League, approached Mary about the Artists for Victory (AFV), founded in 1942, when the U.S. government was actively seeking to connect with the community of artists in and around New York. Its creation was motivated primarily by patriotism and the conviction that there was an important role for art in the war effort on the home front. This was to be demonstrated through AFV’s National War Poster Competition.

Her poster of a little Nazi soldier was accepted and won first prize at a juried exhibition at the Metropolitan Museum of Art, beating out luminaries like Charles Addams, Sol Steinberg, Peter Arno, Sid Hoff and others. She created additional war posters that were part of a nationwide tour to help sell war bonds.