He was a student of Luigi Einaudi, graduating in law with a thesis dedicated to Benjamin Constant, founder of liberalism.
In 1943 he began a clandestine existence with his family in a small village in the Cuneo area between Busca, Caraglio and Dronero.
However, he was captured and sent to the barracks in Via Asti and then transferred to the Le Nuove judicial prison, from where he fortunately managed to escape some time later, by bribing a U.P.I.
[4] Segre joined the armed resistance by enlisting in the 1st Alpine division "Giustizia e Libertà" in Pradleves (Val Grana) and took part in the liberation of Caraglio.
It is in this position that he met Alcide De Gasperi, Ferruccio Parri, Gaetano Salvemini, Piero Calamandrei, Leo Valiani, Giuliano Vassalli and numerous other figures.