The Battle of Caporetto in 1917 (also known as the Twelfth Battle of the Isonzo, the Battle of Kobarid or the Battle of Karfreit as it was known by the Central Powers), took place from 24 October to 19 November 1917, near the town of Kobarid (now in north-western Slovenia, then part of the Austrian Littoral), on the Austro-Italian front of World War I. The battle was named after the Italian name of the town (also known as Karfreit in German).
In August 1917 Paul von Hindenburg decided that to keep the Austro-Hungarians in the war, the Germans had to help them defeat the Italian army. Erich Ludendorff was opposed to this but was overruled. In September three experts from the Imperial General Staff, led by the chemist Otto Hahn, went to the Isonzo front to find a site suitable for a gas attack. They proposed attacking the quiet Caporetto sector, where a good road ran west through a mountain valley to the Venetian plain.
The Austro-Hungarian Army Group Boroević, commanded by Svetozar Boroević, was prepared for the offensive. In addition, a new 14th Army was formed with nine Austrian and six German divisions, commanded by the German Otto von Below. The Italians inadvertently helped by providing weather information over their radio.
Foul weather delayed the attack for two days but on 24 October there was no wind and the front was misted over. At 02:00, 894 metal tubes dug into a reverse slope similar to Livens projectors (Gaswurfminen), were triggered electrically to simultaneously fire canisters containing 600 ml (21 imp fl oz; 20 US fl oz) of chlorine-arsenic agent and diphosgene, smothering the Italian trenches in the valley in a dense cloud of poison gas. Knowing that their gas masks could protect them only for two hours or less, the defenders fled for their lives, though 500–600 were still killed. Then the front was quiet until 06:00 when all the Italian wire and trenches to be attacked were bombarded by mortars.
At 06:41, 2,200 guns opened fire, many targeting the valley road along which reserves were advancing to plug the gap. At 08:00 two large mines were detonated under strong points on the heights bordering the valley and the infantry attacked. Soon they penetrated the almost undefended Italian fortifications in the valley, breaching the defensive line of the Italian Second Army between the IV and XXVII Corps. To protect the attackers’ flanks Alpine Troops infiltrated the strong points and batteries along the crests of the adjoining ridges, Mount Matajur and the Kolovrat Range, playing out their telephone lines as they advanced to maintain contact with their artillery. They made good use of the new German model 08/15 Maxim light machine gun, light trench mortars, mountain guns, flamethrowers and hand grenades.
The attackers in the valley marched almost unopposed along the excellent road toward Italy, some advanced 25 kilometres (16 mi) on the first day. The Italian army beat back the attackers on either side of the sector where the central column attacked, but Below’s successful central penetration threw the entire Italian army into disarray. Forces had to be moved along the Italian front in an attempt to stem von Below’s breakout, but this only weakened other points along the line and invited further attacks. At this point, the entire Italian position was threatened.
The Italian 2nd Army commander Luigi Capello was commanding while bedridden with fever. Realizing that his forces were ill-prepared for this attack and were being routed, Capello requested permission to withdraw back to the Tagliamento. He was overruled by Cadorna who believed that the Italian force could regroup and hold out. Finally, on 30 October 1917, Cadorna ordered the majority of the Italian force to retreat to the other side of the Tagliamento. It took the Italians four full days to cross the river, and by this time the German and Austro-Hungarian armies were on their heels. By 2 November, a German division had established a bridgehead on the Tagliamento. About this time, however, the rapid success of the attack caught up with them. The German and Austro-Hungarian supply lines were stretched to breaking point and consequently they were unable to launch another attack to isolate a part of the Italian army against the Adriatic. Cadorna was able to retreat further and by 10 November had established a position on the Piave River and Monte Grappe, where the last push of the German and Austro-Hungarian forces was met by Italian forces at the First Battle of Monte Grappa.