During his Berlin time, until 1934, he was a member of a group of Socialist and/or Marxist psychoanalysts (with Siegfried Bernfeld, Erich Fromm, Wilhelm Reich, Ernst Simmel, Frances Deri and others).
After his emigration – 1934 to Oslo, 1935 to Prague, 1938 to Los Angeles – he organized the contact between the worldwide scattered Marxist psychoanalysts by means of top secret newsletters ("Rundbriefe").
Those Rundbriefe can be counted among the most important documents pertaining to the problematic history of psychoanalysis between 1934 and 1945, especially in regard to the problem of the expulsion of Wilhelm Reich from the International Psychoanalytic Association in 1934.
[11] Harold Bloom called Fenichel the "grim encyclopaedist of the Freudian psychodynamics"[12] but it was precisely the encyclopedic aspect of his work which aroused the criticism of Lacan.
[16] Although Fenichel himself had warned from the start of his book that he was only offering illustrative examples, not case histories,[17] he may have unwittingly contributed to the vice of attempting to mastermind, not follow and learn from, the analytic process.