The essay aims at reconstructing the history of the University of Florence, from the fall of fascism on July 25th 1943 to the post-World War II period. At the center of this path lies Piero Calamandrei's Rettorato, which began in the summer of 1943 and immediately interrupted by events related to September 8th and the armistice with the Allied powers. As dean of the university, in the aftermath of the Liberation of Florence in August 1944, Calamandrei marked a significant turning point. It was a turning point that not only promptly revived teaching and research functions; but it was also able to provide for the reinstatement of teachers expelled as a result of the racial legislation and for opposition to fascism, along with the beginning of the removals of teachers most involved with the dictatorship. At the same time, in the context of a city deeply involved in the Liberation, the new constitutional order of the Republic began to be drawn; a constitutional project to which Florentine professors - such as Piero Calamandrei and Giorgio La Pira - would offer an outstanding contribution.