The rise of Hitler and other dictators in the 1930s forced numerous Catholic intellectuals to flee Europe; president John O'Hara brought many to Notre Dame. From Germany came Anton-Hermann Chroust (1907–1982) in classics and law, and Waldemar Gurian a German Catholic intellectual of Jewish descent. Positivism dominated American intellectual life in the 1920s onward but in marked contrast, Gurian received a German Catholic education and wrote his doctoral dissertation under Max Scheler. Ivan Meštrović (1883–1962), a renowned sculptor, brought Croatian culture to campus, 1955–62. Yves Simon (1903–61), brought to ND in the 1940s the insights of French studies in the Aristotelian-Thomistic tradition of philosophy; his own teacher Jacques Maritain (1882–73) was a frequent visitor to campus.

What caused many intellectual Catholics to leave europe in the 1930s?