Köhler did not make a public stand against the Nazi regime until the end of April 1933. During the beginning of that month, he still expressed ambivalence as to how serious a threat was posed by the regime. He was wary, but did not become more active against the Nazis until they forced the dismissal of Karl Planck, another well-known experimental physicist. On April 28, 1933, Köhler wrote an article titled "Gespräche in Deutschland" (Conversations in Germany). It was written for the "Deutsche Allgemeine Zeitung" and is officially the last published article that openly attacked the Nazi Regime during their reign.