Once again, the Noyon salient was targeted in the autumn of 1915. As the French accumulated resources in the region in preparation for an assault, the Germans were able to fortify their position, creating a secondary defensive trench line known as the Rückstellung around 2 miles (3 km) back from the front. The total French attacking force of 35 battalions outnumbered the German defence more than 2:1. On 25 September the French attack quickly overran the German front line, which had been shelled with chlorine gas in a number of places. Progress stopped at the Rückstellung, where the majority of German defences were located and artillery fire had not had as much impact due to its location on a slope facing away from the French attack. This line was eventually breeched on 28 September but French casualties meant that progress beyond this point proved too costly to be worth a continued effort.