The Kingdom of Italy () was a state that existed from 1861, when Victor Emmanuel II of Sardinia was proclaimed King of Italy, until 1946, when civil discontent led to an institutional referendum to abandon the monarchy and form the modern Italian Republic. The state resulted from a decades-long process, the Risorgimento, of consolidating the different states of the Italian Peninsula into a single state. That process was influenced by the Savoy-led Kingdom of Sardinia, which can be considered Italy's legal predecessor state. In 1866, Italy declared war on Austria in alliance with Prussia and received the region of Veneto following their victory. Italian troops entered Rome in 1870, ending more than one thousand years of Papal temporal power. Italy entered into a Triple Alliance with the German Empire and the Austro-Hungarian Empire in 1882, following strong disagreements with France about their respective colonial expansions. Although relations with Berlin became very friendly, the alliance with Vienna remained purely formal, due in part to Italy's desire to acquire Trentino and Trieste from Austria-Hungary. As a result, Italy accepted the British invitation to join the Allied Powers during World War I, as the western powers promised territorial compensation (at the expense of Austria-Hungary) for participation that was more generous than Vienna's offer in exchange for Italian neutrality. Victory in the war gave Italy a permanent seat in the Council of the League of Nations. In 1922, Benito Mussolini became prime minister of Italy, ushering in an era of National Fascist Party government known as "Fascist Italy". The Italian Fascists imposed totalitarian rule and crushed the political and intellectual opposition while promoting economic modernization, traditional social values, and a rapprochement with the Roman Catholic Church through the Lateran Treaties which created the Vatican City as a rump sovereign replacement for the Papal States. In the late 1930s, the Fascist government began a more aggressive foreign policy. This included war against Ethiopia, launched from Italian Eritrea and Italian Somaliland, which resulted in its annexation; confrontations with the League of Nations, leading to sanctions; growing economic autarky; and the signing of the Pact of Steel. Fascist Italy became a leading member of the Axis powers in World War II. By 1943, the German-Italian defeat on multiple fronts and the subsequent Allied landings in Sicily led to the fall of the Fascist regime. Mussolini was placed under arrest by order of the King Victor Emmanuel III.