He earned his PhD in 1978 with a study on the German-Italian relations from 1919 to 1944; his scientific advisor was historian Klaus-Jürgen Müller [de].
Geschraten, Verachtet, vergessen" [The Italian Military Internees in the German Sphere, 1943 to 1945: Betrayed, Despised, Forgotten] is considered a standard work on the topic.
[2] Schreiber was one of the first German historians to write about the Waffen-SS and Wehrmacht crimes in Italy, including the Sant'Anna di Stazzema massacre, in his work Deutsche Kriegsverbrechen in Italien.
In Volume III, Schreiber focused on "Hitler's failure to establish true alliances rather than satellite relationships in which Germany always maintained the upper hand".
He notes that the authors are widely read on the topics and are familiar with the existing controversies in the field, expertly guiding the reader through them.