The day after the unit realizes they're stranded on the island, the radio having been damaged in an accident, Sgt Maj Lo Russo misguidedly attempts to raise the soldiers' spirits and whip them into shape, by having them sing "Il Canto degli Italiani", aka "Fratelli d'Italia".
While popular before the Unification, the Kingdom of Italy adopted the Savoy Royal March as its anthem, and it wasn't until after the war, in 1946, that the Canto became Italy's provisional national anthem. It took even longer for it to gain official status, which was ratified in 2017.
Under Mussolini, non-Fascist songs fell out of favor, and were replaced by fascist chants such as Giovinezza, the official hymn of the Fascist Party.