Isonzo (ēzônˈtsō) [key], river, 87 mi (140 km) long, rising in the Julian Alps, NW Slovenia, and flowing S through Slovenia, where it is known as the Soča, then SW through NE Italy before emptying into the Gulf of Trieste. At the entrance to the Venetian plain, the Isonzo valley was the scene of many battles during World Wars I and II. After World War II, the part of the valley above Gorizia, Italy, was given to the former Yugoslavia.
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