(Oct. 24, 1917), Italian military disaster during World War I in which Italian troops retreated before an Austro (Austria-Hungary)-German offensive on the Isonzo front, northwest of Trieste, where the Italian and Austrian forces had been stalemated for two and a half years. In the wake of the successful Austrian and German advance, more than 600,000 war-weary and demoralized Italian soldiers either deserted or surrendered. Total military collapse threatened until November 7, when the Italian line held at the Piave River near Venice, some 70 miles (110 km) from the Isonzo front.

The defeat prompted Italy's allies, France and Great Britain, to send reinforcements and eventually to establish the Supreme War Council to unify the Allied war effort. In Italy the disaster of Caporetto brought about a change in military command and the formation of a new ministry, which reorganized the condition of the home front. The Central Powers' victory was correspondingly ephemeral, because the attack lacked a strategic context.