In August 1915, at the instigation of General Joffre, Commander in Chief of the French Army, Lord Kitchener, Secretary of State, pressed General French, C in C of the BEF for a 'a new offensive in the West… in late September 1915'. The British were then in the process of developing the 'Special Companies' for poison gas warfare. This new strategy encouraged General French to accept the feasibility of an offensive at Loos.
In the five months since the first use of poison gas by the Germans on the 22nd April 1915, 1,347 men - all NCO's - and 57 officers had been selected and trained by Major Charles Howard Foulkes, Royal Engineers, (and now Gas Advisor to the Army) in the new methodology of gas warfare. The first attack was to be based on the release chlorine gas from 190lb high-pressure steel cylinders. These were to be secreted in the front-line trenches, so as to facilitate the penetration of the gas into the German lines and cause the greatest possible number of casualties and confusion.
It was decided that the first British gas attack against the Germans would be at Loos at dawn on the 25th September 1915.
Preparations and execution
During September 1915, 150 tons of chlorine gas in 5,500 high-pressure steel cylinders had been transported across the Channel in unmarked wooden boxes under conditions of great secrecy. For reasons of security, the gas was known only as 'the accessory'. On arrival in France it was transported to Loos by rail. From the railway sidings there, the cylinders were man-handled into the trenches under the highest possible level of security, including aerial surveillance.
By midnight, 24th September 1915, all the cylinders were in place in the forward trenches. Major Foulkes waited at the General Haig's chateau battle headquarters for the order to commence the release of the gas along the 6.5 miles of front from the slagheaps south of Loos to the La Bassée Canal. Haig hesitated as the wind was light, with a tendency to blow towards the British lines. Nevertheless, at 0550 hours on the 25th September 1915, the orders were given to release the gas in the various sectors.
The results were, at best, mixed. In a northern sector the officer commanding the Gas Company, concerned about the wind direction, refused to comply, only to be ordered directly to do so. As he had predicted, the wind was unfavourable and hundreds of the troops in his sector were gassed. In another sector, the keys for turning the release cocks did not fit and only a few cylinders were opened on schedule. The Germans, now forewarned, opened fire and several of the fully charged cylinders exploded releasing the chlorine gas into the British trenches, routing and stampeding the Gas Company personnel. Elsewhere in the northern sector, the wind blew obliquely between the trenches transporting the gas amongst the British and German trenches alike.
In the southern sector, the gas behaved largely as expected, and at 6pm Haig received reports that the gas was rolling over the enemy trenches. Inexplicably, the Germans' gas discipline was generally poor, and the respirators issued to the infantry, ineffective. German commanders reported panic in some trenches, casualties and deaths. By interspersing the releasing of the chlorine gas with smoke, the Gas Companies extended the period of the attack to 40 minutes; a period exceeding the 'operational life' of even the better German gas masks. The smoke added greatly to the confusion and disorientation of the Germans.
The British attack
At 0600 hours, the British infantry of 1 and IV Corps, protected against the chlorine gas by the so-called Hypo helmets, charged into the first German line and were soon 1 mile into the German defences. However, the German response was typically robust and by the time the attack reached the third trench line some of the better protected German machine-gunners were beginning to wreak a considerable toll. Eventually, the British advance ground to halt with a maximum of 3 miles of penetration. Most of the lost ground was regained by the Germans within a week.
Casualties on both sides were high. Overall the Battle of Loos cost the British more than 40,000 casualties - of which some were their finest troops (and included 3 major-generals) - with gas casualties of around 2,600, and 7 gas related deaths. The total Germans losses were only around 20,000, with estimates of 600 deaths due to gassing.