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.
Henri Mordacq
In August 1914, Mordacq was chief of staff of general Archinard's First Reserve Corps Group in the Eastern Army. When the Germans breached the French lines through Belgium, he asked for a frontline command and became commander of the famous 159th Regiment of Alpine Infantry. He immediately took part in the Battle of the Frontiers and his regiment participated in the ending of the German advance in the Vosges before the First Battle of the Marne led to the Race to the Sea. He then took command of the defence of Arras, the "key to the sea" and again halted the German advance there, which led to the stabilization of the front and the beginning of trench warfare.