Born to a Jewish family in Berlin and raised partly in Vienna, Jacob worked for two decades as a journalist and biographer before the rise to power of the Nazi Party.

For twenty years Jacob worked as a journalist and feature writer, also publishing a number of novels, short story collections, and plays.

During the period he earned a reputation as a talented and prolific author, publishing in fields as diverse as news journalism, biography (especially of German composers), dramatic works, fiction, and cultural history.

[2] Following the rise to power of the Nazi Party and the promulgation of laws restricting the freedoms of Jews, Jacob lost his job as a journalist at the Berliner Tageblatt in March 1933.

At the 11th international congress of the literary organization P.E.N., held in Dubrovnik, Jacob joined fellow writers Raoul Auernheimer and Paul Frischaue in vocal opposition to Nazism, and contributed to the fracturing of the Austrian chapter of P.E.N.

The sister of the Austrian poet Ernest Angel, and former wife of the writer Otto Soyka, she enlisted the help of Jacob's American uncle Michael J. Barnes in securing his release on 10 January 1939.

In the United States Jacob resumed his writing career, contributing both to German-language periodicals including the Jewish weekly Aufbau[3] and to the New York Times.