Following the end of the war in 1945, Napolitano joined the Communist Party and suddenly became its federal secretary for Naples and Caserta. In 1947, he graduated in jurisprudence with a final dissertation on political economy, entitled "Il mancato sviluppo industriale del Mezzogiorno dopo l'unità e la legge speciale per Napoli del 1904" ("The lack of industrial development in the Mezzogiorno following the unification of Italy and the special law of 1904 for Naples"). He became a member of the Secretariat of the Italian Economic Centre for Southern Italy in 1946, which was represented by Senator Paratore, where he remained for two years. Napolitano played a major role in the Movement for the Rebirth of Southern Italy for over ten years.