ISONZO, a river in Italy which played a very important part in the World War on the Italian front, no less than twelve battles being named after it. It rises in the Val Trenta, north west of Monte Tricorno, flows through the Plezzo basin in a southerly direction, past Caporetto and Tolmino, through the Canale gorge, between the hills E. of Gorizia and the Podgora Sabotino group opposite, debouches in the plain of Eastern Friuli, until not far from its mouth it divides into two branches, the Sdobba and the Isonzato, both of which flow into the sea in the gulf of Trieste. Before the war the whole of its course was in Austrian territory, but on the outbreak of hostilities the Italian troops crossed it both in the gorge of Plava north of Gorizia, where they established a small bridgehead, and on its lower reaches south of Gradisca. There was very heavy fighting along its banks before the capture of Gorizia and during the operations leading to that capture (August 1916). Between Plava and Salcano and north of Plava the Italians remained on right bank of the river, until the loth battle of the Isonzo in May 1917, when an attack from Plava resulted in the Italian capture of Hill 383, Monte Kuk and Monte Vodice on the left bank. In the
battle (August 17–Sept. 12, 1917) the river was crossed by the Italians north of Plava between Dobar and Anhovo, and Auzza and the Jelenik were conquered, and immediately after the whole of the Bainsizza plateau, some 500 m. above sea level north-east of Gorizia. Higher up the left bank was again in Italian hands, except in the Tolmino sector which it proved impossible to capture in spite of repeated offensives. In October 1917 General Cadorna decided to withdraw all his artillery on the right bank, in view of the coming enemy offensive, but his orders to that effect were not completely carried out. The Austro-Ger mans delivered their attack on October 24, 1917 and broke through the Italian lines first in the Plezzo basin between Sleme and the Mrzli, and crossed the river at Idersko and Caporetto. This breach determined the fall of the positions further south and consequently of the whole Isonzo front, forcing the Italians to fall back on the Piave. The battle positions were reoccupied after the Italian victory of Vittorio in October-November 1918.