The machine gun

Machine guns were extremely important but they were not a war-winning weapon. What the machine gun did do was to strengthen greatly the position of the defender. A machine gun, often positioned in a reinforced concrete blockhouse, could spit bullets at a rate of seven or eight a second. Infantry attacks against such weapons were very costly for the attackers. As the Germans had dug in on foreign (ie French or Belgian) soil, they were content to maintain a defensive line. This forced the British and French to do most of the attacking.

Neil Demarco: Britain and the Great War; Oxford University Press, 1992/2000, page 21