October 18

This Day in History

World War I

Oct 18, 1915:

Third Battle of the Isonzo

On this day in 1915, in the eastern sector of the Italian front in World War I, the Italians launch their third offensive of the year, known as the Third Battle of the Isonzo.

Located in present-day Slovenia, the 60-mile-long Isonzo River ran north to south just inside what was then the Austrian border with Italy, at the head of the Adriatic Sea. The river was flanked by mountains on either side and was prone to flooding, making the terrain especially ill-suited to offensive operations. Nonetheless, it became the most practical spot for Italian forces to attack their Austrian enemy, due to Austro-Hungarian dominance of most other sections of the border.

After the Italian entrance into World War I in late May 1915, Chief of Staff Luigi Cadorna determined that his troops could most effectively strike in the eastern section of the Isonzo region, aiming to capture points on the line from Gorizia to Trieste. For this reason, he poured an immense amount of resources into this area, launching no fewer than 11 offensive operations against the Austrians from June 1915 to September 1917. Like the two attacks that preceded it, the Third Battle of the Isonzo, begun on October 18, 1915, proved disappointing for the Italians. Despite their numerical superiority—19 divisions of troops versus 11 Austrian divisions—Cadorna’s forces failed over two weeks of fighting to capture the two objectives of the attack, Mount Sabotino and Mount San Michele, suffering heavy casualties along the way. All the same, Cadorna waited just one week to begin his next offensive, the Fourth Battle of the Isonzo, effectively an extension of the third.

After the Sixth Battle of the Isonzo in August 1916, the Italians were finally able to establish control of positions at Gorizia, including a long-desired bridgehead across the river. Over the next year, Cadorna tried without much success to extend his army’s gains. In October 1917, however, a combined German-Austrian force inflicted one of the most crushing defeats of the war on the Italians in the Twelfth Battle of the Isonzo, also known as the Battle of Caporetto. In the wake of that battle, Cadorna was replaced by General Armando Diaz, as the Italian focus turned from offensive to defensive operations, with increased help from the other Allied powers. All in all, the Italians suffered some 600,000 casualties over the course of World War I—a full one-half of these came in the Isonzo region.

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