Helmut Flieg or Hellmuth Fliegel was a German writer, known by his pseudonym Stefan Heym. He lived in the United States between 1935 and 1952, before moving back to the part of his native Germany which was, from 1949 to 1990, the German Democratic Republic. He published works in English and German at home and abroad, and despite longstanding criticism of the GDR remained a committed socialist.

https://en.wikipedia.org/wiki/Stefan_Heym