The Italian premier, Vittorio Emanuele Orlando, was a member of the Big Four at the Paris Peace Conference at the end of World War I. His sole interest was to gain control of neighboring territory that he felt was promised in the secret Treaty of London in 1915. That agreement had induced a reluctant Italy to desert the Central Powers and join forces with the Allies. The Italians anticipated establishing their northern border at the Brenner Pass and adding lands on the eastern shore of the Adriatic Sea.
Later, Italian demands were levied upon the city of Fiume (later Rijeka), which was inhabited largely by Croats.
Orlando’s effort to extend Italian control over non-Italians ran counter to Woodrow Wilson’s principle of national self-determination. During often bitter negotiations, the American president took the unprecedented step of making an appeal directly to the Italian people. His effort failed miserably. The Italians were caught up in a wave of nationalism and clearly supported their delegates at the conference. Wilson, who had earlier been greeted as an international savior in Rome, became the object of ridicule.
Wilson reluctantly agreed to the northward Italian expansion, overlooking the fact that the area was home to more than 200,000 German-speaking people. However, he held firm in his opposition to the absorption of Fiume (which remained essentially independent until Italian Fascists staged a coup in 1924). Italian delegates protested Wilson's stance by walking out of the negotiations and remaining absent for two weeks. Wilson was unmoved and Fiume continued as a source of bitterness between the two nations.
See also Wilson's Search for Peace.