23 June 1915: The First Battle of the Isonzo

Isonzo River Viewed from the Austro-Hungarian
Defensive Position

On 24 May, Italian fortresses on the perimeter of the Asiago Plateau fired the first shots of the war on the new front. Supreme Commander Luigi Cadorna mounted a surprise opening offensive, known as Primo Sbalzo [the First Jump], in late May 1915 to improve his army's position in selected sectors. In northeast Italy he ordered an advance across the 1866 border to the banks of the Isonzo. The Second Italian Army, under General Frugoni, captured Caporetto [Kobarid] in the north and the mighty peak of Mte Krn [Mte Nero] beyond the Isonzo. In the south, the Duke of Aosta's Third Army also advanced, but was confronted by enemy units deployed across the river before Gorizia and on its surrounding mountains, thus preventing a quick capture of that key city. It was only in this last sector, however, that Italian territorial ambitions—their sole reason for joining the Allies—could be fulfilled.

The 60- mile-long valley of the Isonzo [Soca] River running from the Julian Alps south to the Adriatic Sea bisected the only practical area for offensive operations by the Italian Army during the Great War. Throughout most of the rest of the mountainous 400-mile length of the S-shaped Italian Front the dominating positions almost everywhere were in the hands of the Austro-Hungarian forces. A Delimitation Commission following the war of 1866 had intentionally given Austria a highly defensible frontier. But by attacking across the coastal plain east of the lower end of the river, they could, so judged Cadorna, feasibly acquire a series of territorial objectives from Gorizia to Trieste down to the Dalmatian Coast. Secondarily, farther to the north they believed they could leapfrog the mountains bracketing both sides of the river and strike a strategic blow against their opponent's rear.

Opening Position for First Battle of the Isonzo

The Isonzo sector, however, presented its own difficult obstacles. The river itself was susceptible to flooding, and the war years featured record rainfalls and snow melts. In the more mountainous northern sector of the front the Italian high command confronted a dilemma they never managed to resolve—to cross the river successfully, they needed to neutralize the forces atop the overlooking mountains; but to occupy those mountains, they had to cross the river first. The lower coastal zone seemed to present more possibilities for advancing, but it featured some peculiar geography that aided defending forces—a plateaued howling wilderness between Gorizia and the Adriatic, known as the Carso.

These disadvantages combined with the Italian determination to achieve their expansionist war aims plus the defensive skills of General Borojevic von Bojna, commander of the Austro-Hungarian Fifth Army, would turn the Isonzo into one of the greatest killing zones of the First World War. Italy would suffer half of their 600,000 killed and Austria-Hungary would suffer 200,000 of its WWI total of 1.2 million dead along the Isonzo. Italian soldier and poet Giuseppe Ungaretti would later write, "The Isonzo scoured me like one of its stones."

Four battles would be fought on this front in 1915, five in 1916, and two in 1917. The First Battle of the Isonzo would begin with a week-long artillery barrage from General Cadorna's forces on 23 June 1915.

Italian Troops During the First Isonzo

The fighting began in similar fashion to the French and British attacks of early World War I on the Western Front with an inadequate, week-long artillery barrage the length of the front. Some early successes were achieved. However, the inability to drive the Austrians from the rest of the high ground west of Tolmino and the river would one day haunt the Italian Army as this bridgehead would be the launch pad for the catastrophic 1917 Caporetto Offensive by the Central Powers. For a few short hours the Italians were able to advance far enough to look down into the streets of Gorizia, but were eventually beaten back. On the Carso they gained small footholds at Adgrado and near Redipuglia and little else.

After failing to make any other significant progress, Cadorna halted on 7 July. He realized his artillery was inadequate, and he was further hindered by a chronic shortage of shells which was never to be resolved. Thus, besides his own flawed strategic thinking, ordnance problems would also limit the offensive capabilities of his armies throughout the war. Nonetheless, he would order three more offensive operations along the Isonzo in 1915.

Source: La Grande Guerra Website