When Italy entered World War I against Austria-Hungary on May 23, 1915, only the Isonzo valley at the southeastern end of the fortified mountain front offered prospects for a major offensive. Here a break through the enemy lines, capturing Gorizia and then Trieste, might lead to an advance across the Ljubljana (Laibach) Gap toward Vienna. General Luigi Cadorna, commanding the Italian army, concentrated two armies (about 200,000 strong) for this enterprise.
Recognizing the critical importance of this sector, the Austro-Hungarians had built fortifications and, despite setbacks in Serbia and Galicia, increased their troops to 100,000 men. In the first four Isonzo battles (June-August 1915), the Italians attacked but were repulsed. Reorganized and bolstered with more artillery, the Italians attacked again in October and yet again in November, also with little success.
In March 1916, Cadorna renewed his attacks in the fifth battle, another failure, and, after having halted an Austro-Hungarian thrust from the Trentino, opened the sixth battle in August, expecting to find an opponent weakened because troops had been shifted to counter the Russian Brusilov offensive. This time Gorizia was taken, but there was no breakthrough. Three more battles followed, but they failed to improve on the initial success.
In 1917, French army mutinies and Russia’s collapse demanded Allied diversionary measures. In response, Cadorna mounted the tenth and eleventh battles. The former stalled, but in the latter (August 18-September 15), shock troops drove the Austro-Hungarians off the strategic Bainsizza Plateau, though exhaustion and supply problems prevented exploitation. Shaken, however, Austria-Hungary requested German support, leading to the Italian disaster at Caporetto, sometimes called the twelfth Isonzo battle.
The Isonzo battles illustrated that well-prepared positions could not be taken by conventional frontal assaults. Each time the Italians had superior numbers and fought bravely, but were held or made only minor advances with heavy losses. Though stretched to the limit, the Austro-Hungarians fought tenaciously on this front with remarkable unity, but they also suffered heavy casualties, which they could afford less than the Italians.
The Reader’s Companion to Military History. Edited by Robert Cowley and Geoffrey Parker. Copyright © 1996 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.