In 1995 Riccardo Di Donato published a series of documents taken from the papers of Arnaldo Momigliano, which wanted to be the start of a reflection on the great historian of antiquity starting from the documentation of his archive. The operation was immediately problematic due to a series of letters and documents that demonstrated the ambiguous position of Momigliano in fascist Italy, not only with respect to regime, for the discovery of his membership in the party, but also in the infighting that troubled Italian Judaism, between pro-fascist anti-Zionists and moderate Zionists in the 1930s to anti-Semitic persecution. A new correspondence found helps us to reconstruct with greater details a dramatic story that has marked in depth the great antichist, highlighting the link between biography and historical research.