Piet Zwart, a Rotterdam-based designer and typographer, began his career working in the tradition of the Arts and Crafts movement, but radically reoriented his work in 1917 under the influence of the avante-garde De Stijl group. Through his De Stijl contacts, Zwart met Kurt Schwitters, El Lissitsky, and Jan Tschichold, all of whom were developing a modernist mode of graphic design, combining the technique of photomontage with geometric Constructivist elements. In the 1920s and '30s, Zwart produced advertisements in this idiom for prominent clients such as NKF (the Dutch cable works) and PTT (the Dutch postal service). He was a member of the Circle of New Advertising Designers, a group of designers founded by Schwitters, who shared similar experimental interests. In addition to his commercial design projects, Zwart was also involved in leftist politics and the Dutch worker-photography movement.