Immediately to the south of Pulteney's Third Corps, and extending from Bécourt in the north to a point opposite Fricourt village, lay Horne's Fifteenth Corps. The general task of this Corps was to attack Mametz on the right, contain Fricourt in the centre, and attack between there and La Boiselle towards Mametz Wood. It consisted of the Twenty-first, the Seventh, and the Seventeenth Divisions. Of these, the most northerly was the Twenty-first, that fine North-country division which had so terrible an ordeal when it came up in support upon the second day of Loos. Those who held that in spite of defeat its conduct upon that occasion was soldierly, were borne out by its achievement on the Somme, where it made a lodgment in the enemy's line upon the first {77} day, and did good service at later stages of the battle. Let us now turn our attention to its advance. It may first be mentioned that the units were the same as those enumerated in the description of Loos, save that in each brigade one regular battalion had been substituted. Thus the 1st Lincolns, 4th Middlesex, and 1st East Yorks took the place of the 8th East Yorks, 12th West Yorks, and 14th Durhams respectively. The 50th Brigade of the Seventeenth Division was attached to the Twenty-first Division for the purpose of the attack, and will be included with it in this summary of the operations. The rest of the Seventeenth Division was in reserve. The attack was on a three-brigade front, the 64th Brigade upon the north, just south of La Boiselle, and in close touch with the Thirty-fourth Division. To the right of the 64th was the 63rd Brigade, and to the right of that the 50th, which advanced straight upon Fricourt. The 62nd Brigade was in reserve. It will be best to deal with the attack of the 64th Brigade with some detail, as its exploits had a very direct bearing upon the issue of the battle.