Italy had been allied with the German and Austro-Hungarian Empires since 1882. Italy had its own designs against Austrian territory in the Trentino, Istria, and Dalmatia, and maintained a secret 1902 understanding with France, which effectively nullified its previous alliance commitments. Italy refused to join Germany and Austria-Hungary at the beginning of the war because their alliance was defensive. The Austrian government started negotiations to obtain Italian neutrality in exchange for French territories namely Tunisia, but Italy joined the Triple Entente by signing the London Pact in April and declaring war on Austria-Hungary in May 1915; it declared war against Germany 15 months later.
Picture 1: Italian officers on the Dolomites mountains
In general, the Italians had numerical superiority but were poorly equipped. The Italians went on the offensive to relieve pressure on the other Allied fronts and achieve their territorial goals. In the Trentino-South Tyrol front, the Austro-Hungarian defense took advantage of the elevation of their bases in the mostly mountainous terrain, which was not suitable for military offensives. After an initial Austro-Hungaric strategic retreat to better positions, the front remained mostly unchanged, while Austrian Kaiserschützen and Standschützen and Italian Alpini troops fought bitter, close combat battles during the summer and tried to survive during the winter in the high mountains. The Austro-Hungarians counterattacked in the Altopiano of Asiago towards Verona and Padua in the spring of 1916, known as the Strafexpedition, but they also made little progress.
Picture 2: Italian Troops holding a position on the Piave Front, June 191
Beginning in 1915, the Italians mounted 11 major offensives along the Isonzo River north of Trieste, known as the First through Eleventh Battles of the Isonzo. These attacks were repelled by the Austro-Hungarians who had the higher ground. In the summer of 1916, the Italians captured the town of Gorizia. After this minor victory, the front remained practically stable for over a year, despite several Italian offensives. In the fall of 1917, thanks to the improving situation on the Eastern front, the Austrians received large reinforcements, including German assault troops. The Central Powers launched a crushing offensive on October 26 that was spearheaded by German troops and supported by the Austrians and Hungarians. The attack resulted in the victory of Caporetto; the Italian army was routed, but after retreating more than 60 miles, it was able to reorganize and hold at the Piave River. In 1918 the Austrians repeatedly failed to break the Italian line and, decisively defeated in the Battle of Vittorio Veneto, surrendered to the Entente powers in November.