He created his most famous work in 1917, a poster to encourage recruitment in the United States Army during World War I. It showed Uncle Sam pointing at the viewer (inspired by a British recruitment poster showing Lord Kitchener in a similar pose) with the caption “I Want YOU for U.S. Army”. Flagg had first created the image for the July 6, 1916 cover of Frank Leslie's Illustrated Newspaper with the headline “What Are You Doing for Preparedness?” Over four million copies of the poster were printed during World War I, and it was revived for World War II. Flagg used his own face for that of Uncle Sam (adding age and the white goatee), he said later, simply to avoid the trouble of arranging for a model. President Franklin Delano Roosevelt praised his resourcefulness for using his own face as the model. By some accounts though, Flagg had a neighbor, Walter Botts, pose for the piece.