In 1914 Erwin Schrödinger achieved habilitation ("venia legendi"). Between 1914 and 1918 he participated in war work as a commissioned officer in the Austrian fortress artillery (Gorizia, Duino, Sistiana, Prosecco, Vienna). In 1920 he became the assistant to Max Wien, in Jena, and in September 1920 he attained the position of ao. Prof. ("ausserordentlicher Professor"), roughly equivalent to Reader (UK) or associate professor (US), in Stuttgart. In 1921, he became o. Prof. ("ordentlicher Professor", i.e. full professor), in Breslau (now Wrocław, Poland).