The Battle of Loos was fought in September 1915. The battle at Loos was part of Marshal Joffre's campaign in Artois that was designed to push back the Germans in a two-pronged offensive. Hence why on September 25th the British 1st Army commanded by Douglas Haig attacked German positions at Loos.
1915 had not been a particularly successful year for the Allies. There had been no decisive advance on the Western Front where trench warfare remained dominant. The Allies were also still reeling from the disaster at Gallipoli and the Germans were inflicting continuing major damage on the Russian Army on the Eastern Front. Joffre, pictured above, wanted to launch a joint British-French attack on the Germans in Artois, the success of which would do a great deal to boost the morale of the Allies with the ultimate goal of delivering a decisive blow against the Germans. One prong of Joffre's attack would be carried out solely by the French with an attack on the Germans in Champagne. A joint British-French attack in Artois involved the British attacking just north of Lens at Loos with the French 10th Army attacking the German south of Lens.
When Haig toured the region to the north of Lens he found that the land was flat and open to German machine gun fire. He feared heavy losses. He relayed his fears of major casualties to Joffre but the French Marshal was not prepared to change his plans. Kitchener told Haig that co-operation was essential, though he did recognise that the British might experience heavy losses.
With such pressure put on him, Haig had to come up with a plan for the attack at Loos. He decided to attack in a very narrow frontage so that the British could concentrate their fire to its maximum extent against German machine guns. Haig's plan was simple - concentrated British artillery fire and pinpoint infantry fire would give the advancing British troops sufficient cover.
However, in the lead up to the attack, another weapon became available to Haig - poison gas. He realised that such a weapon would neutralise the German machine gunners. As a result he decided to widen the attack front as he was convinced that he had a weapon that would be devastating.
However, Haig faced one major problem - he was ordered to co-ordinate his attack with that of the French. He was told that he could only attack on September 25th and no earlier. He decided to build a degree of flexibility into his plan. In fact, Haig came up with two plans for the attack at Loos. If the weather was good (i.e. the wind was blowing in the right direction) he would order an attack on a wide front using gas across the whole front. His second plan was to attack on the 25th on a narrow front if the weather was not good and gas could not be used. A follow-up attack on the wider front with poison gas would occur in the immediate days after the 25th if the weather permitted.
With such flexibility built into his attack, Haig was confident of success. British forces attacked the Germans early on September 25th. The French attacked over five hours later.
An artillery attack on the German lines had started on September 21st and 250,000 shells were fired at the German positions. On the 24th Haig was given the news that the predicted weather for the 25th was favourable and he ordered that poison gas would be used. Weather reports very early on the 25th indicated that the weather was "changeable" and Haig was advised to release the gas as soon as was possible. At 05.15 Haig ordered the release of chlorine. However, from the front line reports came back that the wind was too calm for the gas to be released. Those in the front lines got the order back that gas was to be used.
At 05.50 gas was released from pressurised cylinders. The release of chlorine gas occurred on and off over a 40 minute period. The infantry attack started at 06.30.
In some places the attack was very successful - the 15th Division got into Loos and took the town after nighttime street fighting. However, in some areas, lack of communication caused problems. At the La Bassée Canal, the officer in charge of releasing the chlorine failed to do so as he did not believe that the conditions were right. He only turned on the pressurised gas cylinders when he was ordered to do so - and poisoned 2,632 of his own men - with seven fatalities.
The British had a tolerably good first day but failed to follow up their successes. Why?
To succeed, the British had to send in reserve divisions to consolidate the work done by those who had fought in the initial assault. The divisions held in reserve (the 21st and 24th and commanded by Sir John French) comprised of raw recruits who had only arrived in France in September. The two divisions were held too far away from Loos to have any impact. Simply to get to the battle zone, they had to march miles - 50 miles in four days. Haig had assumed that the 2 reserve divisions would move up to the front as soon as the infantry had started their attack at 06.30. This did not happen. They arrived too late to have any impact on the success of the British on Day 1. They were also extremely tired from their marching - even Haig called them "poor fellows". Haig blamed Sir John French for the delay in their arrival.
What is certain is that when the reserves got to the front at Loos, their inexperience meant that they could not cope with the German counter-attack and the British, having gone from near success, narrowly avoided a retreat only as a result of the arrival of the Guards Division. Between September 26th and September 28th, the British lost many men to German machine gun fire as they attacked German positions around Loos without the aid of artillery support.
The battle effectively ended on September 28th. The British suffered 50,000 casualties while the Germans lost about 25,000 men.