After the German defeat in World War II, Oehler was imprisoned by Soviet occupation forces and died c. March 1946 in an improvised prison in Weimar.
Oehler took part in the Battle of Tannenberg (1914) early in World War I, but soon became unable to fight due to a case of sciatica.
In 1919, Oehler left the military with the rank of Major and went to work with Elisabeth Förster-Nietzsche at the Nietzsche-Archiv, beginning in April.
They had all shared an opposition to the democratic Weimar Republic and had been more or less sympathetic towards the Conservative Revolutionary movement and the rise of Fascism.
[1] Nevertheless, Oehler and his wife were members of Hermann Graf Keyserling's anti-militarist "Schule der Weisheit".
Following Elisabeth Förster-Nietzsche's death, it became known within the Archiv that she had forged some documents and anecdotes relating to her brother Friedrich; this fact was not made public, however.
[2] The United States Army occupied Weimar in 1945, at the close of World War II, and later handed the city over to Soviet forces.
Oehler attempted to defend the Nietzsche-Archiv from the charge of having supported the Nazi regime, claiming that it always had been politically neutral.
As the family later found out, he had been sentenced to penal labour in Siberia but had died, probably of hunger or freezing, in an improvised prison while still in Weimar.