(See also: Third Battle of Artois and Second Battle of Champagne) The Battle of Loos was a World War I battle that took place from 25 September – 13 October 1915 in France on the Western Front, during the First World War. It was the biggest British attack of 1915, the first time that the British used poison gas and the first mass engagement of New Army units. The French and British tried to break through the German defences in Artois and Champagne and restore a war of movement. Despite improved methods, more ammunition and better equipment, the Franco-British attacks were contained by the German armies, except for local losses of ground. British casualties at Loos were about twice as high as German losses.