At the beginning of World War I, Bruchmüller was recalled to active duty and soon became artillery commander of the 86th Division on the Eastern Front. In 1915 he fought in thirteen actions, winning the Iron Cross First Class and Second Class. The Russians conducted the Lake Naroch Offensive from 18–30 March 1916. For the counter-attack, Bruchmüller persuaded the commander of the Tenth Army, "Generaloberst" Hermann von Eichhorn, to centralize the artillery command. Bruchmüller planned to lead the infantry attack with a creeping barrage, which contributed to the German victory, for which he was awarded the Pour le Mérite, Germany's highest military award, in 1917 (one of only four senior artillery officers to receive this honor during the war).