How did the Italian government change between WWI and WWII as noted in the nonfiction book, War in Val D'Orcia, 1943-1944?

Italy was/is a relatively new country, having consisted for centuries of a collection of city/states and only formulated into a single entity in the mid-1800's. A member of the Allied forces in World War I, it was taken over by Mussolini and Fascism in the early 1920's.