As fighting continued around Arras and Festubert, and after the repulse of the German offesive at Ypres in May, the overall allied commander, Field Marshal J.J.C. Joffre, devised a new offensive aimed at breaking the German lines in three places, the Champagne Valley, Artois, and Loos. The Loos offensive would be left to the British First Army under Gen. Douglas Haig.
Gen. Haig, concerned about the withered condition of the British army, as well as the shortage of artillery shells, tried to postpone the attack. He eventually gave into pressure from Joffre and agreed to the offensive. In addition to artilley support, Haig would also be allowed the use of poison gas to make up for his lack of shells. The attack began on the 25th of September.
Immediately, the battle turned into a disaster for the British. The initial artillery barrage consisted of a massive gas assault which was caught in the wind and blown immediately on the British infantry as it advanced. Several casualties mounted from this mistake and the attack lost momentum. The artillery began a regular assault on the German lines but had little effect. However, the British still managed to take parts of the German lines after a fierce struggle. The 1st Division was given the task of taking an area of the German defenses known as "Lone Pine" which was supposedly lightly garrisoned following the artillery attack. The British, confident of this information, were butchered advancing into the German machine gun cross fire. "Lone pine" was never taken by the British.
The second day of fighting, the British called up two of its "New Army" divisions to assault the German trenches at Hulluch and Hill 70. The divisions were beaten back with severe casualties and forced to withdraw. The Guards division tried a renewed counter atttack with the remnants of one of the 21st "New Army" division and were again beaten back. The action died off after that final failing attack.
By the 28th, the fighting at Loos had ended. By the 8th of October, the Third Battle of Artois and Second Battle of Champagne had also ended with about the same result. The British had suffered 60,000 casualties. After the battle, the French lost control of the British forces and Gen. Haig became Commander in Chief of the British Army.