Ernst Thalmann Memorial stamp, 1954 -- Stamps of the GDR #34
Stamp in memory of the tenth anniversary of the murder of the great leader of the KPD from 1925 to 1933. In 1933 he was arrested by the Nazis and spent much of the next 11 years in solitary confinement in prison before being killed in August, 1944 in Buchenwald concentration camp on the direct orders of Hitler.
Why didn't Stalin get him out during the pact with Hitler. Anton, Spanish Communists leader was got out "After the German invasion of France, at Ibárruri's request the Russians obtained Antón's release and transfer to Moscow." https://en.wikipedia.org/wiki/Francisco_Ant%C3%B3n#:~:text=Francisco%20Ant%C3%B3n%20Sanz%20(also%20Paco,War%20(1936%E2%80%931939).
Rakosi was got out as well "After returning to Hungary in 1924, he was imprisoned, but he was released to the Soviet Union in 1940, in exchange for the Hungarian revolutionary banners captured by Russian troops at Világos in 1849.[16]". https://en.wikipedia.org/wiki/M%C3%A1ty%C3%A1s_R%C3%A1kosi