Thanks To The Treaty Of Vienna
Both parties signed the Treaty of Vienna in 1866 and enjoyed relative peace for a long time. In truth, they had been comrades since the commencement of hostilities in July 1914. However, as the complicated battle extended over the area, longstanding animosity between the two began to resurface.
After The Treaty Of London
By signing the Treaty of London in 1915, Italy broke away from the Triple Alliance it had created with Germany and Austria-Hungary. This meant that the two entities separated by the Stelvio Pass were at odds. Mount Scorluzzo, which separated them, aided them much in the war.