Well up, toward the north, in the Dolomites there followed considerable fighting, in the Cordevole Valley particularly, for the Col di Lona, the loftiest of the mountain tops in that region. The Cordevole unites with the Val Forsa some twenty miles east of the Adige Valley, the Val Forsa connecting with the Adige at the town of Lavio, six miles north of Trent. To cut in behind the Austrians south of Trent would, of course, have created havoc with the entire Austrian forces in the Trentino, but, as stated, the defensive possibilities of the situation are so formidable that success would appear almost beyond the realms of actuality. On the Isonzo front the fighting all along continued on a large scale. An idea of the immensity of the struggle is suggested by the Austrian estimate in January, 1916, that Italian casualties had passed the million mark. Exaggerated as this number was regarded in allied circles, it showed Austria-Hungary's opinion of the severity of the fighting in what was considered a subsidiary theatre of the Great War. The railroad situation on the Isonzo front is, as in practically all modern military situations, of primary strategic importance. The Istrian Peninsula is served by three lines, each of which runs to Austrian bases of supply. One runs up the valley of the Isonzo, through Gorizia and Tolmino and through the Hochein Tunnel to Vienna. At Gorizia a branch leaves this line, running southeast, and connects Gorizia with Trieste across the Carso Plateau. The second line comes from the east from Laibach through San Pietro, where a branch runs south to Fiume, and the third comes north from the Austrian naval base at Pola. Gorizia is served by the northern road from Vienna, from Trieste by the main line, and by the branch just described. Supplies from Vienna would be stopped by cutting the road anywhere north of Gorizia. But to shut off Trieste as a source, both of the southern rail communications must be cut. Early in June, 1915, the Italians forced a passage of the Isonzo at Plava and at Monfalcone, and cut the railroad at these two points. Gorizia then continued to be supplied only by the Trieste branch. Nor was Trieste itself cut off, as the road from Laibach through San Pietro continued open. The only way to isolate Istria was to take the San Pietro junction, and this was the ultimate aim of the operations at that region.