Battle of Caporetto, 1917: the breakthrough on the Isonzo

Caporetto is the Italian name of Kobarid, a small town on the Soča river, the Isonzo of Italian maps, in today's Slovenia; the Germans called it Karfreit. The battle named after it is also called the Twelfth Battle of the Isonzo.²

Background: eleven battles on the Isonzo

Italy entered the First World War against Austria-Hungary in May 1915. Its commander in chief, General Luigi Cadorna, attacked along the Isonzo eleven times, at a heavy cost, and gained less than seven miles, about a third of the way to Trieste. After the Eleventh Battle in August 1917 the Austrian positions near Gorizia were close to collapse.³

Vienna asked Berlin for help. Paul von Hindenburg and Erich Ludendorff of the German Supreme Command agreed with the Austro-Hungarian chief of staff, Arthur Arz von Straussenburg, on a joint offensive, and Germany sent seven divisions to the upper Isonzo. General Otto von Below commanded the Austro-German attack force. Cadorna saw the build-up from the air and called off his own planned offensive to prepare defenses, but bad weather delayed the attack and the Italians were still caught by surprise.⁴

24 October: gas at Bovec and the breakthrough

The attack fell on the front between Bovec (Flitsch, Plezzo) in the north and Tolmin (Tolmein) in the south. At Bovec the Germans used a new weapon. According to the historian Simon Jones, at about 2 a.m. on 24 October pioneers fired 894 gas projectors at a ravine behind the Italian front; 818 bombs, about 6.5 tonnes of phosgene in all, landed in it, and the 600 to 800 Italian soldiers holding it were found dead.⁵

Elsewhere a short, heavy bombardment came before the infantry, who used grenades and flamethrowers to work through the shattered Italian lines. By nightfall on 24 October they had advanced about 25 kilometers. On 25 October Below's troops reached the Torre river, and the Italian armies began to fall back.⁶

The retreat to the Piave

What started as a local breach became a general retreat. The Central Powers broke through at Bovec and Tolmin and pushed into the Friulian plain. By mid-November the Italians had been driven back about 60 miles to the Piave river, some 30 kilometers north of Venice.⁷

There the line held. Cadorna was removed and on 9 November General Armando Diaz took his place. Diaz fought a defensive war and relied more on Italy's stronger allies. According to EBSCO's Research Starters, Below's attacks on the Piave were beaten off, and his last attempt, on 23 November, failed to break the line. British and French troops joined the Italians on the river at the end of November, and the German divisions were later recalled to the Western Front.⁸

Casualties: how many men did Italy lose?

The losses are disputed, and the argument is mostly about prisoners and deserters, not the dead. History.com counts almost 700,000 Italian casualties: about 40,000 killed or wounded, 280,000 captured and 350,000 deserted. The World of the Habsburgs, a project of the Austrian state palaces, gives the same 40,000 casualties and 280,000 prisoners of war, but only tens of thousands of deserters. Either way, far more Italian soldiers were captured or scattered than were killed.⁹

Why Caporetto mattered

In Italy the defeat brought anger and fear into the open. History.com notes that violent anti-war protests peaked after the battle. According to the World of the Habsburgs, mutinies and protests in Turin and Milan were put down by the army with shootings, punishments and death sentences, yet the defeat also hardened national resistance, and Italy now fought a defensive war with more men mobilized and allied help.¹⁰

For Austria-Hungary the victory was less of a gain than it looked. Hundreds of thousands of prisoners had to be fed while its own cities ran short of food and fuel. The Austro-Hungarian offensive on the Piave in June 1918 failed, and by the late summer of 1918 two thirds of its divisions were at half strength.¹¹