The paper provides an analysis of Martin Buber’s intellectual conversion and shows how it facilitates a deeper understanding of the phenomenon of nationalism. Buber, who is today known mainly as a key representative of dialogical philosophy, was in the 1910s part of the double wave of German and Jewish nationalism which strongly affected the German-speaking Jewish public. Buber provided intellectual support for this wave of nationalism and interpreted World War I as a unique chance for the spiritual unification of European (...) Jewry. Consequent to his conflict with Gustav Landauer Buber underwent a complex intellectual and existential transformation. He abandoned key concepts of his pre-dialogical thought and laid the foundations of his dialogical thought. He rejected his endorsement of Geman nationalism and substantially reevaluated his political positions. The analysis of Buber’s intellectual development sheds light on some important aspects of the dynamics of nationalism. (shrink)