Politician and writer, he began his antifascist militancy when he was just seventeen, in response to the Matteotti murder. In 1927 he was arrested in a bar in Milan because he was considered a dangerous element by Mussolini's regime. From that time, Spinelli began a long period of imprisonment in Fascist jails, also being imprisoned in Ventotene, an island of confinement for political dissidents during the dictatorship. There, Spinelli drafted, along with Eugenio Colorni and Ernesto Rossi, For a Free and United Europe. A Draft Manifesto, better known as the Ventotene Manifesto. A revolutionary document, which laid the political and ideological foundations of the future union between European states. Released from prison in 1943, Spinelli became one of the main animators of the battles in favor of European integration, devoting the rest of his life to politics. 

A plaque will be dedicated to Altiero Spinelli at the Garden of the Righteous of the World in Milan on 6 March 2024.