Triple Alliance, defense arrangement between Austria-Hungary, Germany, and Italy in the late 19th and early 20th centuries. In 1882 the 3 nations pledged mutual help if any of them were attacked by 2 or more other nations. Germany and Austria-Hungary signed an agreement in 1879 at the prompting of German chancellor Otto von Bismarck, and Italy joined them 3 years later. Serbia also joined in 1882 and Romania in 1883; the name remained Triple Alliance because the 2 Balkan nations were not considered major powers. The alliance was renewed several times before the outbreak of World War I in 1914, but actually broke up when the war started: Italy and Romania fought on the side of the Allies—France, Great Britain, and Russia (the Triple Entente).
See also: World War I.