After September 8, 1943, he sought refuge in Switzerland (where he met European intellectuals, politicians and critics), then in 1944 he returned to fight with the partisans in Valdossola.
[2] Soon after the Russian invasion of Hungary in 1956, Fortini left the Italian Socialist Party which he had joined in 1944.
From 1964 to 1972 he taught in secondary schools, and from 1976 occupied the Chair of Literary Criticism at the University of Siena.
During this period he had considerable influence on younger generations in search of social and intellectual change.
Fortini translated works by Goethe, Brecht, Simone Weil, Milton, Proust, Kafka, Éluard, Frénaud, Flaubert, Gide and many others.