Italy declares war on Austria-Hungary

On Sunday 23 May 1915, at about a quarter past three in the afternoon, the Italian ambassador in Vienna, Duke Giuseppe Avarna, handed the declaration of war to the Austro-Hungarian Foreign Minister, Baron István Burián. The Kingdom of Italy, which for more than thirty years had been an ally of the Habsburg monarchy in the Triple Alliance, entered the fight on the side of the Entente.

The declaration

The note was short. In it the Italian government recalled that on 4 May it had already informed Vienna why it considered the alliance to have been broken by Austria-Hungary, and that it had declared it void, regaining full freedom of action. Now, determined to defend Italy’s rights and interests by every means and to realise its “national aspirations”, it declared in the name of the King that from the following day Italy considered itself to be at war with Austria-Hungary. The ambassador added that the Austro-Hungarian ambassador in Rome, Baron Karl von Macchio, was receiving his passports that same day, and asked to be given his own. The Foreign Minister, Sidney Sonnino, at the same time notified Italian missions abroad and the governments of other states of the state of war.

Behind the declaration lay a decision taken many weeks earlier. On 26 April Prime Minister Antonio Salandra and Sonnino had signed an agreement with the Entente in London, in which Italy undertook to enter the war within a month in return for the promise of Trentino, Trieste, Istria and part of Dalmatia. The government crisis of mid-May ended in victory for the supporters of war. On 20 May the Chamber of Deputies, and on 21 May the Senate, granted the government full powers for the duration of the war, and the King signed the law on 22 May.

Mobilisation

Also on 22 May Victor Emmanuel III proclaimed the general mobilisation of the army and the fleet, and 23 May was its first day. Twelve north-eastern provinces, among them Udine, Belluno, Verona and Vicenza, were declared a war zone. The army was not starting from scratch. A partial, concealed mobilisation had been under way since the spring, and units had been gathering on the frontier for weeks. At the head of the army stood its Chief of the General Staff, General Luigi Cadorna.

A perfidy “such as history does not know”

In Vienna Rome’s decision was no longer a surprise. That same day, a little over an hour after Avarna’s visit to the ministry, Emperor Franz Joseph I issued the manifesto “To My Peoples!”. “The King of Italy has declared war on Me,” he wrote. “A perfidy such as history does not know has been committed by the Kingdom of Italy against its two allies.” After an alliance lasting more than thirty years, during which Italy had been able to enlarge its territory and flourish, it had, as the Emperor wrote, abandoned its allies in the hour of danger and gone over “with flying colours” to the camp of their enemies. The sense of betrayal was widespread in the monarchy. Historians note that the war with Italy, unlike the war with Russia or Serbia, found sincere support also among the Slovenes and Croats, whose lands had been promised to Rome.

War only with Austria

Italy declared war only on Austria-Hungary. The Treaty of London obliged it to fight all the enemies of the Entente, but Rome wanted to avoid a direct clash with Germany, with which it had strong economic ties, among other things. The German ambassador, Prince Bernhard von Bülow, asked for his passports and soon left Rome (according to German sources as early as the evening of 23 May), but formally the two states were not at war for more than a year. Italy declared war on Turkey in August 1915, and on Germany only in August 1916.

A new front

Hostilities began on the night of 23/24 May. At dawn the Austro-Hungarian fleet bombarded Ancona and other towns on the Adriatic coast, and Italian troops crossed the frontier. The Italian front opened that day ran across the Alps from the Stelvio Pass to the Adriatic coast. The bloodiest fighting was to take place on the Soča (Isonzo), where eleven battles were fought by the autumn of 1917, before the twelfth came, ending in the Italian defeat at Caporetto. The war, which Rome had chosen in the hope of quick gains, lasted three and a half years and, according to various estimates, cost Italy between about 600,000 and 650,000 soldiers killed and dead.