French went sick in September, Robertson acting as Commander-in-Chief BEF. Both GHQ and First Army persuaded themselves that the Loos attack could succeed, perhaps as the use of gas, whose use by the Germans at Second Ypres had been condemned by Sir John, would allow a decisive victory. Sir John decided to keep a strong reserve consisting of the Cavalry Corps, the Indian Cavalry Corps and Haking's XI Corps, which consisted of the Guards Division and two New Army Divisions (21st and 24th) just arrived in France. French was privately doubtful that a breakthrough would be achieved and was concerned that in the event of failure the government would want to "change the bowler" (letters to Winifred 18 and 21 September). Haig (and Foch) wanted the reserves close to hand to exploit a breakthrough on the first day; French agreed to deploy them closer to the front but still thought they should be committed on the second day.