 In May 1919 , upon receiving an invitation from fellow Jewish artist Marc Chagall , Lissitzky returned to Vitebsk to teach graphic arts , printing , and architecture at the newly formed People 's Art School – a school that Chagall created after being appointed Commissioner of Artistic Affairs for Vitebsk in 1918 . Lissitzky was engaged in designing and printing propaganda posters ; later , he preferred to keep quiet about this period , probably because one of main subjects of these posters was the exile Leon Trotsky . The quantity of these posters is sufficient to regard them as a separate genre in the artist 's output . 
