After returning to civilian life, Hilberg chose to study political science, earning his Bachelor of Arts degree at Brooklyn College in 1948. He was deeply impressed by the importance of elites and bureaucracies while attending Hans Rosenberg's lectures on the Prussian civil service. In 1947, at one particular point in Rosenberg's course, Hilberg was taken aback when his teacher remarked: "The most wicked atrocities perpetrated on a civilian population in modern times occurred during the Napoleonic occupation of Spain." The young Hilberg interrupted the lecture to ask why the recent murder of 6 million Jews did not figure in Rosenberg's assessment. Rosenberg replied that it was a complicated matter, but that the lectures dealt only with history down to 1930, adding, "History doesn't reach down into the present age." Hilberg was amazed by this highly educated, German-Jewish emigrant passing over the genocide of European Jews in order to expound on Napoleon and the occupation of Spain. Moreover, Hilberg recalled, it was an almost taboo topic in the Jewish community, and he pursued his research as a kind of 'protest against silence'.