1925 Leow was elected the Second Chairman of the Roter Frontkämpferbund (RFB), founded in 1924, the defense and protection organization of the KPD.

Later SPD politician Herbert Wehner, who was himself a communist in the Weimar period, wrote decades later in his memoirs that Leow was "a thoroughly corrupt person".

In 1936, he was arrested during the Stalinist purges and sentenced to death on 3 October 1937 for organizing a Trotskyist-terrorist group in the Military Collegium of the Supreme Court of the USSR, and was shot.

[2] In the history of the German Democratic Republic Leow was in the first decades after his death a so-called Damnatio Memoriae; he was deliberately concealed in the history of the GDR and in the public culture of remembrance of the East German state: His person was deliberately not mentioned and traces of his existence have been systematically eliminated from published documents and image reproductions of the GDR.

The reason for this practice was that the arrest and murder of Leow (a German communist and refugee from fascism) by the Soviet sister state did not fit into the historical picture of the GDR, and therefore his publications were not allowed to be distributed.