Kelsen accepted a professorship at the University of Cologne in 1930. When the National Socialists came to power in Germany in 1933, he was removed from his post. He relocated to Geneva, Switzerland where he taught international law at the Graduate Institute of International Studies from 1934 to 1940. During this time period, Hans Morgenthau departed from Germany to complete his habilitation dissertation in Geneva, which resulted in his book "The Reality of Norms and In Particular the Norms of International Law: Foundations of a Theory of Norms". By remarkable good fortune for Morgenthau, Kelsen had just arrived in Geneva as a professor and he became an adviser for Morgenthau's dissertation. Kelsen was among the strongest critics of Carl Schmitt because Schmitt was advocating for the priority of the political concerns of the state over the adherence by the state to the rule of law. Kelsen and Morgenthau were united against this National Socialist school of political interpretation which down-played the rule of law, and they became lifelong colleagues even after both had emigrated from Europe to take their respective academic positions in the United States. During these years, Kelsen and Morgenthau had both become "persona non grata" in Germany during the full rise to power of National Socialism.