The first year of the Austro-Italian war had seen no real impression made on Austria's mountain defences, and even in the valley of the Isonzo Gorizia still forbade an Italian advance on Trieste. The Italian line was the worst possible for defence, and it depended for its security upon the fact that the bulk of the Austrian forces were involved in Russia and in the Balkans. The front was on the Isonzo, but a flank of over 200 miles invited a thrust down one of the various passes towards Venice which, if successful, would cause the whole front to collapse like a pack of cards; and marvellous though the feats of Italian valour and mechanical ingenuity had been in the mountain fighting throughout the winter, they had not wrested the passes from Austria's hands. The attack was preceded by a bombardment which began on 14 May, and the scene selected lay on a line drawn from Trent to Venice through the Sette Communi, Posina, and Pasubio. The flanks held fairly firm, but the centre gave way, and on the 20th-24th the line was withdrawn on the left to Posina and Pasubio. Things were no better in the Sette Communi on the right, but west of Pasubio the Italians stopped the Austrian advance in the pass of Buole on 30 May. On the same day, however, they had to evacuate Arsiero and Asiago, south of the Sette Communi. But by now Cadorna had got his reinforcements, and on 3 June he announced that the Austrian offensive was checked. The attack was, however, renewed on the 13th, and the Austrians advanced to within four miles of Valstagna and the railway running down the Brenta valley to Padua. They got no farther, and before the end of June Cadorna began his counter-offensive. By that time the thoughts of the Austrians and most of their troops were elsewhere; and just as the German campaign at Verdun was ruined by the Entente offensive on the Somme, the Austrian advance from the Trentino was stopped by the Russian attack in the East. In the first week of June Brussilov had gone through the Austrian lines like brown paper at Lutsk and Dubno.