But while the Italians were unable to capture this position, when General Boroevics took his troops out of their defenses and sent them charging across the open ground, he found that the enemy had made good use of his precarious hold on the edges of the tableland. Although they occupied barely more than the rim of the plateau, with the flooded Isonzo a third of a mile broad beneath them, the Italians had strengthened their positions with sandbag intrenchments and hauled up a few pieces of light artillery. The chief support of the infantry holding these sandbag defenses was the heavy guns across the river, which searched out the Austrian columns whenever they left cover. In weight of artillery the Italians had the advantage, for most of the Austrian 12-inch howitzers were busy in the Alps, and they had to depend mainly upon 6-inch pieces. By the second week in July, 1915, the Austrians relaxed their efforts, and the Italians began a slow advance, working up the hills overlooking Gorizia by a variety of methods. In the places, comparatively few, where there was cultivated ground, they practiced the siege method of sapping forward, but generally their advance was over bare rock, where trenches could be excavated only by the use of dynamite, and when a charge was made the troops had to carry sandbags to build temporary cover from machine-gun fire. This method of warfare, in fact, was general throughout the whole mountain front, where the hard rock carried a mere veneer of earth, and sandbags had to serve for defense until the engineers could blast trenches and galleries in the flintlike face of the slopes. The repulse of the Austrian counterattack in the middle of July, 1915, ended the first phase of the battle of Gorizia. On July 18th, 19th and 20th, General Cadorna delivered a fierce assault aided by knowledge gained in the first stage of the battle, which, for the Italians, was little more than a reconnaissance in force. For three days and nights he drove the troops of his combined Second and Third Armies against the enemy's lines all along the Isonzo. His system was to attack by day and then at night resist the enemy's counterassaults on his newly won positions. The Italians retained all the ground they won during these days of terrific fighting, and captured 3,500 prisoners. By the 20th of July their confidence had increased to such an extent that they determined upon a night assault. But next morning Cadorna received word from his aeroplane scouts and his spies that the enemy was massing for a supreme effort. The Italian advance was stayed and every man was set at work helping the engineers strengthen the trenches.