حرب الخنادق
Trench warfare was also new for the Germans, whose training and equipment were designed for a mobile war to be won in six weeks, but they quickly adapted their weapons to the new situation. Siege howitzers now lobbed massive shells into the Allied trenches. Skilful use of trench mortars and hand and rifle grenades (first used against British troops on 27 September), enabled the Germans to inflict great losses upon Allied troops, who had neither been trained nor equipped with these weapons. Searchlights, flares and periscopes were also part of the German equipment intended for other purposes, but put to use in the trenches.