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.

On the day of the attack, the engineers manning the poison gas cylinders warned not to use them, citing the weakness and unpredictability of the wind.
When overruled by Lt-General Hubert Gough the gas drifted back into the British lines and caused more British than German casualties.
Though one division did break through the German defences on the first day (25 September), French had positioned reserves too far to the rear, and they only reached the front line by night.
Wanting to be closer to the battle, French had moved to a forward command post at Lilliers, less than 20 miles behind First Army's front.
 He left Robertson and most of his staff behind at GHQ and had no direct telephone link to First Army.
 Haig's infantry attacked at 6.30 am on 25 September and he sent an officer by car requesting release of the reserves at 7 am—he did not hear until 10.02 am that the divisions were moving up to the front.
 French visited Haig between 11 –11.30 and agreed that Haig could have the reserve, but rather than using the telephone he drove to Haking's Headquarters and gave the order personally at 12.10 pm.
 Haig then heard from Haking at 1.20 pm that the reserves were moving forward, but by the time the men, already exhausted from an overnight march in the rain, reached the front line through the chaos of the battlefield they were committed against strengthened German positions the following morning.

Joffre sent a letter of congratulation (26 September)—Clive sensed that Joffre did not really believe the British attack would succeed but wanted it kept going as a diversion from Champagne, although after complaints from Sir John that the French Tenth Army were not doing enough Foch ordered them to take over some line from the British around Loos.
When the British reserves were ordered to attack on the second day (26 September), the advancing divisions found unbroken barbed wire and intact and ungassed German defenses.
The slaughter that day resulted in 7,861 British casualties without a single German casualty.

Sir John was still keen for a concerted Anglo-French attack, telling Foch (28 September) that a gap could be "rushed" just north of Hill 70, although Foch felt that this would be difficult to co-ordinate and Haig told him that First Army was not in a position for further attacks at the moment.
 Charteris wrote that "Sir John French is played out.
The show is too big for him and he is despondent."

The Battle of Loos was a strategic and tactical failure and has become one of the epitomes of a Great War battle in which generals showed complete disregard for the situations on the front lines the soldiers were facing.
With only 533 guns and a shortage of shells to cover a wide 11,200 yard front with two German trench lines to bombard, the British would likely be attacking positions that had not been disrupted enough to allow a breakthrough.
The British commanders at this time did not grasp that German tactical doctrine called for the second line of machine gun nests to be situated on the reverse slope of their hillside defenses; destroying them would need artillery with higher trajectories and shells with high exp
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. 
On the day of the attack, the engineers manning the poison gas cylinders warned not to use them, citing the weakness and unpredictability of the wind. When overruled by Lt-General Hubert Gough the gas drifted back into the British lines and caused more British than German casualties. Though one division did break through the German defences on the first day (25 September), French had positioned reserves too far to the rear, and they only reached the front line by night. Wanting to be closer to the battle, French had moved to a forward command post at Lilliers, less than 20 miles behind First Army's front.  He left Robertson and most of his staff behind at GHQ and had no direct telephone link to First Army.  Haig's infantry attacked at 6.30 am on 25 September and he sent an officer by car requesting release of the reserves at 7 am—he did not hear until 10.02 am that the divisions were moving up to the front.  French visited Haig between 11 –11.30 and agreed that Haig could have the reserve, but rather than using the telephone he drove to Haking's Headquarters and gave the order personally at 12.10 pm.  Haig then heard from Haking at 1.20 pm that the reserves were moving forward, but by the time the men, already exhausted from an overnight march in the rain, reached the front line through the chaos of the battlefield they were committed against strengthened German positions the following morning.
Joffre sent a letter of congratulation (26 September)—Clive sensed that Joffre did not really believe the British attack would succeed but wanted it kept going as a diversion from Champagne, although after complaints from Sir John that the French Tenth Army were not doing enough Foch ordered them to take over some line from the British around Loos. When the British reserves were ordered to attack on the second day (26 September), the advancing divisions found unbroken barbed wire and intact and ungassed German defenses. The slaughter that day resulted in 7,861 British casualties without a single German casualty.
Sir John was still keen for a concerted Anglo-French attack, telling Foch (28 September) that a gap could be "rushed" just north of Hill 70, although Foch felt that this would be difficult to co-ordinate and Haig told him that First Army was not in a position for further attacks at the moment.  Charteris wrote that "Sir John French is played out. The show is too big for him and he is despondent."
The Battle of Loos was a strategic and tactical failure and has become one of the epitomes of a Great War battle in which generals showed complete disregard for the situations on the front lines the soldiers were facing. With only 533 guns and a shortage of shells to cover a wide 11,200 yard front with two German trench lines to bombard, the British would likely be attacking positions that had not been disrupted enough to allow a breakthrough. The British commanders at this time did not grasp that German tactical doctrine called for the second line of machine gun nests to be situated on the reverse slope of their hillside defenses; destroying them would need artillery with higher trajectories and shells with high exp
John French, 1st Earl of Ypres