Start of the Third Battle of the Isonzo

On 18 October 1915, precisely at noon, the Italian artillery opened fire along the whole front on the Isonzo, from the snow-covered peaks of the Krn massif to the Adriatic coast. Thus began the Third Battle of the Isonzo, the first autumn offensive of General Luigi Cadorna. The Austrian official history writes that when this “hurricane” of fire from guns of every calibre rolled over the valley, the defenders no longer had any doubt that the third battle had begun. It was also something new on this front. The infantry did not go over to a great assault that day. The bombardment was to last three days and destroy the Austro-Hungarian positions before the divisions went in on 21 October.

Eleven weeks of preparation

Since the end of the Second Battle of the Isonzo in August, the Italians had been bringing their bled-white divisions back up to strength and gathering artillery. Cadorna had concluded that the earlier attacks had failed above all for lack of heavy guns and ammunition. Heavy batteries were brought in from the fortresses of Verona and Venice, from the fortifications on the Tagliamento and from the Tyrolean front, and French howitzers and naval guns arrived. According to the Italian official history, cited by the Austrian one, the Second and Third Armies and the reserve of the supreme command together had 338 battalions and 1,372 guns, including 305 heavy and medium ones. Other works give about 1,200–1,250 guns. By 17 October a million shells had been stockpiled. The infantry received more machine guns, heavy trench mortars, steel helmets and shields.

Paris and London were pressing the Italians to attack as soon as possible and relieve Serbia, which the Central Powers had attacked on 6 October. Cadorna, however, did not want to begin before he had gathered his ammunition. Domestic politics also counted. After five months of war enthusiasm had clearly waned, strikes were breaking out in the industrial districts, and public opinion was waiting for the capture of Gorizia.

Plan and forces

The plan envisaged that strong wings would first push the defenders off the two salients of the front on either side of Gorizia. In the north the Second Army of General Pietro Frugoni was to break out of the bridgehead at Plava onto the heights of the Bainsizza plateau, and in the south the Third Army of the Duke of Aosta was to take Monte San Michele and the edge of the Karst plateau. Only then was the frontal assault on the Gorizia bridgehead, between Mount Sabotino and the Podgora hill, to follow. Further north, IV Corps was to attack the Krn massif and the Tolmin bridgehead for the third time.

The Austro-Hungarian Fifth Army of General Svetozar Boroević knew what was coming. Since the beginning of October radio interception, airmen, prisoners and deserters had been reporting new batteries and concentrations of troops. The Austrians recognised as a fake a supposed order of the Italian Second Army halting attacks until the spring, which had been planted on them through the legation in Bern. From 14 to 17 October Italian regiments carried out reconnaissance in force against the forward positions of the 20th Honvéd Division at Monte San Michele, and on the afternoon of 17 October the artillery began shelling the Tolmin bridgehead. On the Isonzo Boroević had 12 divisions, that is 137.5 battalions, about 128,600 rifles and 634 guns. The strength of the Italians was estimated at 300,000–350,000 rifles.

The first day

The fire fell on trenches, wire entanglements, reserve positions, approach roads, headquarters and batteries. On the first day it did not yet manage to destroy most of the shelters and obstacles. Only the projecting salient of the front on the Karst, shelled from several sides, suffered more heavily. In the afternoon strong Italian detachments struck several times at the forward positions on the northern slope of Monte San Michele, and on the upper Isonzo at the slopes of Krn and Vodil vrh. By evening all these attacks had been repulsed. Austrian airmen reported very lively troop movements behind the Italian front, and at night near Ronzina the Italians could be heard bringing pontoons up to the river.

The bombardment continued for the next two days, with a short pause at noon on 19 October. On the morning of that same day Italian bombers dropped more than a hundred bombs on the Austrian airfield near Gorizia. On 20 October heavy mortars began destroying the wire on Sabotino and Podgora, while the defenders on the Karst were already lying without cover in shell craters. The great infantry assault they had been waiting for came only on 21 October. For this reason some works count the Third Battle of the Isonzo from that day. The Italian and Austro-Hungarian official histories, however, count it from 18 October, from the first shot of the three-day artillery preparation.