The birth of the Italian Republic (officially on June 2, 1946) is a key event of Italian contemporary history. Until 1946, Italy was officially a monarchy ruled by the House of Savoy, kings of Italy since the Risorgimento (and previously of Sardinia). However, Benito Mussolini, enjoying the support of the monarchy, imposed fascism after the October 28, 1922 March on Rome, eventually engaging Italy in World War II alongside Nazi Germany. In 1946, Italy became a republic after the results of a popular referendum. Monarchists advanced suspicions of fraud that were never proved. A Constituent assembly was elected at the same time.