Trench warfare
Trench warfare has become archetypically associated with the First World War of 1914–1918, when the Race to the Sea rapidly expanded trench use on the Western Front starting in September 1914. By the end of October 1914 the whole front in Belgium and France had solidified into lines of trenches, which lasted until the last weeks of the war. Mass infantry assaults were futile in the face of artillery fire as well as rapid rifle and machine-gun fire. Both sides concentrated on breaking up enemy attacks and on protecting their own troops by digging deep into the ground. Trench warfare also took place on other fronts, including in Italy and at Gallipoli.
Infiltration tactics
As far back as the 18th century, Prussian military doctrine stressed maneuver and force concentration to achieve a decisive battle (). The German military searched for ways to apply this in the face of trench warfare. Captain Willy Rohr fought in the long Battle of Hartmannswillerkopf (1914–1915), starting with two "Pionier" (combat engineer) companies. Such engineers often employed non-standard weapons and tactics compared to the regular infantry. Rohr's initial efforts to use these as special advanced strike teams, to break French lines for following troops to exploit, achieved only limited success, with heavy losses. Rohr, working with his superiors, saw equipment improved, including the new "Stahlhelm" (steel helmets), ample supplies of hand grenades, flamethrowers, light mortars and machine guns. Rohr's analysis was that much more training was needed to incorporate the new weapons and to coordinate separate attacks as needed to achieve the overall operational goals. His analysis got the attention of the "Oberste Heeresleitung" ("OHL", German army high command). In December 1915, Rohr was given the task of training the army in "modern close combat", and soon promoted to major. During the next two years, special stormtrooper detachments were created in divisions throughout the army; select men were sent to Rohr for training, who became trainers when they returned to their units. These tactics were expanded and refined by many in the German military command, extending the Prussian military doctrine down to smallest units—specially trained troops maneuvered and massed to assault positions, wherever opportunities were found.