The Battle of Loos took place from 25 September to 8 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 in the north and Champagne at the south end of the Noyon Salient and restore a war of movement.