Upon the return of the liberal politician Giovanni Giolitti to the Italian government in June 1920, during the Biennio Rosso, the official attitude towards the Kingdom of Italy's regency of Carnaro, which had been constituted in Fiume, began to waver.

D'Annunzio refused to accept an ultimatum by Italian General Enrico Caviglia to abandon Fiume and claimed the Treaty of Rapallo as illegal and his Regency declared war on Italy.

Since D'Annunzio's legionnaires were refusing to surrender and were strongly resisting the attack using machine guns and grenades, the Italian dreadnoughts Andrea Doria and Duilio opened fired on Fiume and bombed the city for three days.

On 5 October 1921, Riccardo Zanella became the first and only elected president of the short lived Free State of Fiume, but that was unable to end disputes over the city.

The period of diplomatic tension ended with the Treaty of Rome on 27 January 1924, which assigned Fiume to Italy and Sušak along with other villages, to Yugoslavia, with joint port administration.