In Denmark Geiger began by gaining a scholarship from the Rockefeller Foundation through the "Instituttet for Historie og Samfundskonomie" in Copenhagen; later he gave lectures at the University of Copenhagen. From 1938 - 1940 he was professor of sociology at the University of Århus—Denmark's first ever professor of sociology. When German troops entered the city in 1940 he was forced to leave, escaping to Odense where he lived with his parents-in-law for the next few years. In 1943 he fled once again to Sweden where he stayed for three years. Here he gave lectures at the Universities of Stockholm, Uppsala and Lund. When the war ended in 1945, Geiger immediately returned to Århus, taking up his position as professor of sociology once more. His first step was to found the university institute for research into societies, the first institute of its kind in Scandinavia.