There he attended the grammar school at the monastery of Unser Lieben Frauen (Our Dear Lady) in Magdeburg and was baptised a Protestant in St John's Church at the age of 11.
Though he was later expelled from the University of Kiel during the Gleichschaltung of Nazi Germany, Jacoby is said by some to have been one of a very small number of German Jews who initially supported Adolf Hitler.
According to some witnesses, he even went so far as to make the startling comparison in 1933: As a Jew I find myself in a difficult position.
In 1939, Jacoby fled to England, where he stayed at Oxford, continuing his work on the fragments of the Greek historians.
Also significant is his long entry in the Realencyclopädie der Classischen Altertumswissenschaft on the Greek historian Herodotus; written in 1913, this article established many of the questions that would come to dominate modern Herodotean scholarship.