Erich Hahn [SEP] conflict
Erich Hahn
Oberleutnant Erich Hahn was a World War I flying ace credited with six aerial victories.
Biography.
Erich Hahn was born on 18 October 1891 in Leipzig, the Kingdom of Saxony, in the German Empire.
He joined Saxony's Infantry Regiment Nr. 2 just before World War I. In 1913, he learned to fly at Anthony Fokker's flying school. As one of the very few experienced pilots about, he was serving in "Flieger-Abteilung" (Flier Detachment) 64 when the war
under the supervision of Erich Hecke. 
He became interested in differential geometry; he edited Wilhelm Blaschke's 2nd volume about that issue, and both made an acclaimed contribution to the Jena DMV conference in Sep 1921.
In October 1922 (or 1923) he was appointed assistant professor at the University of Vienna. While there he became familiar with the work of Wilhelm Wirtinger on knot theory, and became closely connected to Hans Hahn and the Vienna Circle. Its manifesto (1929) lists one of Reidemeister's publications in a