We then entered upon a contest lasting for many weeks, during which the enemy, having found his strongest defenses unavailing, and now fully alive to his danger, put forth his utmost efforts to keep his hold of the main ridge. This stage of the battle constituted a prolonged and severe struggle for mastery between the contending armies, in which, although progress was slow and difficult, the confidence of our troops in their ability to win was never shaken. Their tenacity and determination proved more than equal to their task, and by the first week in September they had established a fighting superiority that has left its mark on the enemy, of which possession of the ridge was merely the visible proof. [Sidenote: The plateau gained.] [Sidenote: Successes of the French south of the Somme] The way was then opened for the third phase, in which our advance was pushed down the forward slopes of the ridge and further extended on both flanks until, from Morval to Thiepval, the whole plateau and a good deal of ground beyond were in our possession. Meanwhile our gallant allies, in addition to great successes south of the Somme, had pushed their advance, against equally determined opposition and under most difficult tactical conditions, up the long slopes on our immediate right, and were now preparing to drive the enemy from the summit of the narrow and difficult portion of the main ridge which lies between the Combles Valley and the River Tortille, a stream flowing from the north into the Somme just below Peronne. [Sidenote: Careful artillery preparation.] Defenses of the nature described could only be attacked with any prospect of success after careful artillery preparation. It was accordingly decided that our bombardment should begin on June 24, 1916 and a large force of artillery was brought into action for the purpose. [Sidenote: Gas discharges.] Artillery bombardments were also carried out daily at different points on the rest of our front, and during the period from June 24 to July 1, 1916, gas was discharged with good effect at more than forty places along our line upon a frontage which in total amounted to over fifteen miles. Some seventy raids, too, were undertaken by our infantry between Gommecourt and our extreme left north of Ypres during the week preceding the attack, and these kept me well informed as to the enemy's dispositions, besides serving other useful purposes. [Sidenote: Attack by the Royal Flying Corps.] On June 25, 1916, the Royal Flying Corps carried out a general attack on the enemy's observation balloons, destroying nine of them, and depriving the enemy for the time being of this form of observation. [Sidenote: British and French co-operate in attack.] On July 1, 1916, at 7.30 a. m., after a final hour of exceptionally violent bombardment, our infantry assault was launched. Simultaneously the French attacked on both sides of the Somme, co-operating closely with us.