In English the first major discussion of the topic was in the 1940s by Kurt Lewin, who was Lessing's colleague at the University of Berlin in 1930. Lewin emigrated from Germany to the United States in 1933, and though focused on Jews also argued for a similar phenomenon among Polish, Italian and Greek immigrants to the USA. Lewin's was a theoretical account, declaring that the issue "is well known among Jews themselves" and supporting his argument with anecdotes. According to Lewin, a self-hating Jew "will dislike everything specifically Jewish, for he will see in it that which keeps him away from the majority for which he is longing. He will show dislike for those Jews who are outspokenly so, and will frequently indulge in self-hatred." Following Lewin's lead, the concept gained widespread currency. "The 1940s and 1950s were ‘the age of self-hatred’. In effect, a bitter war broke out over questions of Jewish identity. It was a kind of ‘Jewish Cold War’..." in which questions of Jewish identity were contentiously debated. The use of the concept in debates over Jewish identity – for example over resistance to the integration of African Americans into Jewish neighbourhoods – died down by the end of the 1970s, having been "steadily emptied of most of its earlier psychological, social, and theoretical content and became largely a slogan."