Battle of Caporetto

Between 24 October and 19 November 1917, an Austro-Hungarian and German offensive broke through the Italian lines on the upper Isonzo river around the town the Italians called Caporetto, today Kobarid in Slovenia. Also known as the Twelfth Battle of the Isonzo, it drove the Italian army back some 150 kilometres to the Piave river and cost Italy hundreds of thousands of men, most of them taken prisoner. It remains a byword in Italy for catastrophic defeat, and it brought down both a government and a commander-in-chief.

Through 1917 Italy had launched repeated offensives against Austria-Hungary along the Isonzo, the eleventh of which pushed the defenders back further than any before. Fearing that his exhausted army would crack, Emperor Karl asked Kaiser Wilhelm II for German help. In August Hindenburg and the Austro-Hungarian chief of staff Arz von Straußenburg agreed to move troops from the Eastern Front, over Ludendorff's objections.

In September a German team that included the chemist Otto Hahn surveyed the front for a gas attack and picked the quiet Caporetto sector, where a good road led west through a valley towards the Venetian plain. A new 14th Army, combining Austro-Hungarian and German divisions under the German general Otto von Below, was formed for the blow, while Svetozar Boroević's forces would attack further south towards the Adriatic.

After two days' delay for bad weather, the attack opened in the early hours of 24 October. At 2 a.m., near Bovec, 894 buried projectors fired canisters of poison gas into the Italian trenches; with masks good for two hours at most, the defenders fled, and perhaps 500 to 600 were killed. A mortar bombardment followed, then at 6.41 a.m. some 2,200 guns opened fire, and at 8 a.m. infantry advanced after mines were blown under positions on the heights.

The attackers quickly pierced the thinly held valley defences of the Italian Second Army. Specially trained assault units, armed with light machine guns, mortars, flamethrowers and grenades, led the way, while mountain troops worked along the ridges on either side. Some units advanced 25 kilometres on the first day. Among the junior officers who distinguished themselves was Erwin Rommel.

The Second Army's commander, Luigi Capello, ill with fever, asked to fall back to the Tagliamento, but the chief of staff Luigi Cadorna refused until 30 October. The crossing took four days under constant pressure. The attackers won a bridgehead over the Tagliamento on 2 November, but their supply lines were now overstretched and their troops underfed and exhausted. By 10 November Cadorna had formed a new line on the Piave and Monte Grappa, which held.

Italian casualties were around 13,000 dead and 30,000 wounded, with between 265,000 and 275,000 captured, many of whom gave themselves up willingly after months of harsh discipline. Over 3,000 guns were lost. The attackers suffered about 70,000 casualties. Italy's effective army shrank from about 1.8 million to 1 million men, and some 600,000 civilians were displaced.

Paolo Boselli's government fell, and Cadorna, already loathed by his troops, was dismissed and replaced by Armando Diaz. Allied leaders met at Rapallo on 5 to 7 November and agreed to create a Supreme War Council, while French and British divisions were rushed to Italy. Under Diaz the army rebuilt. It threw back a final enemy push at Monte Grappa in late 1917 and contained an Austro-Hungarian offensive across the Piave in June 1918. On the anniversary of Caporetto it launched the Vittorio Veneto offensive, which broke the Austro-Hungarian army and was followed by an armistice on 3 November 1918, ending the fighting on Italy's front in the First World War. The defeat entered Italian language and politics: Mussolini later mocked the failed socialist strike of 1922 as the socialists' Caporetto, and Ernest Hemingway drew on the retreat in A Farewell to Arms.

Our 1914 map shows the Isonzo valley inside Austria-Hungary, close to its border with Italy. Kobarid and the battlefield now lie in Slovenia.