In the lead-up to World War I, the Kingdom of Italy faced a number of short-term and long-term problems in determining its allies and objectives. Italy's recent success in occupying Libya as a result of the Italo-Turkish War had sparked tension with its Triple Alliance allies, the German Empire and Austria-Hungary, because both countries had been seeking closer relations with the Ottoman Turkish Empire. In Munich, Germans reacted to Italy's aggression by singing anti-Italian songs.
Italy's relations with the French Third Republic also were in bad shape: France felt betrayed by Italy's support of Prussia in the Franco-Prussian War, opening the possibility of war erupting between the two countries. Italy's relations with the United Kingdom of Great Britain and Ireland had also been impaired by constant Italian demands for more recognition in the international stage following the occupation of Libya, and its demands that other nations accept its spheres of influence in East Africa and the Mediterranean. The area between British Egypt and the firmly held Italian territories is the region of southern Cyrenaica which was under dispute of ownership between Italy and the United Kingdom.
In the Mediterranean, Italy's relations with the Kingdom of Greece were aggravated when Italy occupied the Greek-populated Dodecanese Islands, including Rhodes, from 1912 to 1914. These islands had been formerly controlled by the Ottoman Empire. Italy and Greece were also in open rivalry over the desire to occupy Albania.
King Emmanuel III himself was uneasy about Italy pursuing distant colonial adventures, and said that Italy should prepare to take back Italian-populated land from Austria-Hungary, as the "completion of the Risorgimento". This idea put Italy at odds with Austria-Hungary. A major hindrance to Italy's decision on what to do about the war was the political instability throughout Italy in 1914. After the formation of the government of Prime Minister Antonio Salandra in March 1914, the government attempted to win the support of nationalists and moved to the political right.
At the same time the left became more repulsed by the government after the killing of three anti-militarist demonstrators in June. Many elements of the left including syndicalists, republicans and anarchists protested against this and the Italian Socialist Party declared a general strike in Italy. The protests that ensued became known as " Red Week" as leftists rioted and various acts of civil disobedience occurred in major cities and small towns such as seizing railway stations, cutting telephone wires, and burning tax-registers. However only two days later the strike was officially called off, though the civil strife continued. Militarist nationalists and anti-militarist leftists fought on the streets until the Italian Royal Army forcefully restored calm after having used thousands of men to put down the various protesting forces following the invasion of Serbia by Austria-Hungary in 1914, World War I broke out.
Despite Italy's official alliance to the German Empire and in the Triple Alliance, she initially remained neutral, claiming that the Triple Alliance was only for defensive purposes. In Italy, society was divided over the war: Italian socialists generally opposed the war and supported pacificism, while nationalists militantly supported the war. Long-time nationalists Gabriele D'Annunzio and Luigi Federzoni and an obscure Marxist journalist and new convert to nationalist sentiment, future Fascist dictator Benito Mussolini, demanded that Italy join the war.
For nationalists, Italy had to maintain its alliance with the Central Empires, in order to obtain colonial territories in expenses of France. For the liberals, the war presented Italy a long-awaited opportunity to use an alliance with the Entente to gain certain Italian-populated and other territories from Austria-Hungary, which had long been part of Italian patriotic aims since unification. In 1915, relatives of Italian revolutionary and republican hero Giuseppe Garibaldi died on the battlefield of France, where they had volunteered to fight. Federzoni used the memorial services to declare the importance of Italy joining the war, and to warn the monarchy of the consequences of continued disunity in Italy if it did not: Mussolini used his new newspaper Il Popolo d'Italia and his strong oratorical skills to urge nationalists and patriotic revolutionary leftists to support Italy's entry into the war to gain back Italian populated territories from Austria-Hungary, by saying "enough of Libya, and on to Trent and Trieste”.
Mussolini claimed that it was in the interests of socialists to join the war to tear down the aristocratic Hohenzollern dynasty of Germany which he claimed was the enemy of all European workers. Mussolini and other nationalists warned the Italian government that Italy must join the war or face revolution and called for violence against pacifists and neutralists. Left-wing nationalism also erupted in southern Italy, socialist and nationalist Giuseppe De Felice Giuffrida saw joining the war as essential to relieving southern Italy of the rising cost of bread which had caused riots in the south, and advocated a "war of revolution".
With nationalist sentiment firmly on the side of reclaiming Italian territories of Austria-Hungary, Italy entered negotiations with the Triple Entente. The negotiations ended successfully in April 1915 when the London Pact was brokered with the Italian government. The pact ensured Italy the right to attain all Italian-populated lands it wanted from Austria-Hungary, as well as concessions in the Balkans and the division of German colonies along France and England in Africa. The proposal fulfilled the desires of Italian nationalists and Italian imperialism, and was agreed to. Italy joined the Triple Entente in its war against Austria-Hungary.
The reaction in Italy was divided: former Prime Minister Giovanni Giolitti was furious over Italy's decision to go to war against its former defence allies Austria-Hungary. He claimed that Italy would fail in the war, predicting high numbers of mutinies, Austro-Hungarian occupation of more Italian territory, and that the failure would produce a catastrophic rebellion that would destroy the liberal-democratic monarchy and the liberal-democratic secular institutions of the state.