German physician, polygraph, astrologer and politician, known for his publication Charakter-Konstellation: Mit besonderer Berücksichtigung der Gleichgeschlechtlichkeit (1929; “Character Constellation: With Particular Reference to Homosexuality”) which attempts to unite psychology and astrology and create a framework for determining the degree of homosexuality of a person based upon the constellation of stars at the time of his birth.
The son of a court clerk and bank director, his youth was spent in Dortmund. He enlisted in the Prussian Army and until the end of 1918 participated in World War I, being deployed on the Western Front – finishing with the rank of lieutenant.
Between August and November 1924 Heimsoth wrote at Rostock his dissertation entitled “Hetero- und Homophilie” (“Heterophile and Homophile”), which was devoted to homosexuality. With this work, Heimsoth was probably the first to introduce the term “homophilia” in sexology.
The thesis argued that in certain erotic and friendly relationships there are certain norms looked for and desired which are “the same”. This homophilia can occur both in relationships between men and between women. In contrast, Heimsoth saw heterophilia as a relationship characterized by “the opposite”; considered well within the range of heterophilia are platonic relationships between an effeminate man and a masculine man. He basically tried to prove that a masculine man could want another masculine man, because there were esoteric and friendly connections in such a relationship which were not wanted nor looked for in the other sex, but rather in the same sex, as an opposite pole.
After obtaining his doctorate, Heimsoth worked at practices in the Gynaecologic University Clinic of Kiel. At the same time, he became an “activist of the first homosexual emancipation movement”, but distanced himself from the Scientific-Humanitarian Committee that had formed around Magnus Hirschfeld, because he considered that the theories advocated by the Committee concerning the “third sex” were wrong. In his writing Freundesliebe oder Homosexualität (“Love Between Friends or Homosexuality”), published in the magazine Der Eigene by Adolf Brand in 1925, Heimsoth showed his antisemitism. Heimsoth’s ideal was that of a whole man, virile and Aryan.
From 1925 to 1928 Heimsoth learned astrology from the frigate captain Friedrich Schwickert in Vienna. Heimsoth’s 1929 publication Charakter-Konstellation is dedicated to Schwickert.
In 1928 Heimsoth wrote a letter to Ernst Röhm. Röhm, convicted of treason following his participation in the Munich Beer Hall Putsch, had quarreled with Hitler. Excerpts from Röhm’s book Geschichte eines Hochverräters, published in 1928, were read “between the lines” by Heimsoth as recognition of the author’s homosexuality.
Röhm and Heimsoth met in person in 1928. In subsequent letters from Röhm, it can be deduced that they had conversations about very personal issues and were together at gay meeting places in Berlin. Heimsoth subsequently deposited Röhm’s letters in the safe of a lawyer. In 1930 Röhm became head of the SA. From April 1930, Munich prosecutors investigated Röhm for “unnatural fornication”. On 10 July 1931 the Berlin Police requisitioned Röhm’s letters in a search of his house; Heimsoth was interrogated. Towards late 1931 and early 1932, the Secretary of State for the Interior of Prussia, Wilhelm Abegg, informed the social democrat publicist Helmuth Klotz of the existence of the letters. Along with an extensive press report, Klotz published the letters in March 1932.
At the time of the correspondence with Röhm, it appears that Heimsoth became a member of the NSDAP (Nazi Party). According to Otto Strasser, Heimsoth was not only an active member of the Nazi Party in the following years, but a “burning National Socialist”. In June 1931 Strasser warned the police about the existence of Röhm’s letters. Heimsoth dropped out of the Nazi Party.
Heimsoth joined the Communist Party of Germany (KPD), led by Beppo Römer. Heimsoth was a member of the Executive Committee (Leiko) of the Aufbruch-Arbeitskreise (AAK) focused around the magazine Aufbruch published by Römer. The AAK was an attempt by the KPD to win over circles of intellectuals and military officers as allies in their fight against Nazism.
After the Machtergreifung, the Nazi Seizure of Power, Heimsoth continued giving information to the KPD secret service. A September 1933 Gestapo report indicates continued contact with Beppo Römer. In early July 1934, Heimsoth was shot dead by an SS command in Berlin, as part of the purge carried out during the so-called Night of the Long Knives, in which Hitler got rid of political enemies both real and imagined.

Link to Wikipedia biography