From 1920 to 1922, Sorge lived in Solingen, in present-day North Rhine-Westphalia, Germany. He was joined there by Christiane Gerlach, the ex-wife of Kurt Albert Gerlach, a wealthy communist and professor of political science in Kiel, who had taught Sorge. Christiane Gerlach later remembered about meeting Sorge for the first time: "It was as if a stroke of lightning ran through me. In this one second something awoke in me that had slumbered until now, something dangerous, dark, inescapable...". Sorge and Christiane married in May 1921. In 1922, he was relocated to Frankfurt, where he gathered intelligence about the business community. In the summer of 1923, he took part in the "Erste Marxistische Arbeitswoche" ("First Marxist Work Week") Conference in Ilmenau. Sorge continued his work as a journalist and also helped organize the library of the Institute for Social Research, a new Marxist think tank in Frankfurt.