The 15th Reserve Division fought on the Western Front, participating in the opening German offensive which led to the Allied Great Retreat, fighting at Sedan in late August 1914. It fought in the First Battle of the Marne. Thereafter, it remained in the line in the Champagne region and fought in the Second Battle of Champagne in September–October 1915. It fought on the Aisne until September 1916, and then joined the Battle of the Somme. Its next major engagement was the Battle of Arras in the Spring of 1917. In May 1917, the division was transferred to the Eastern Front, where it resisted the Russian Summer Offensive known as the Kerensky Offensive. It remained on the Eastern Front until the armistice on that front, and then returned to the Western Front, arriving in the Verdun region at the beginning of January 1918. It went to the Flanders/Artois region in April 1918 and remained in that general area until the end of the war. Allied intelligence rated the division as third class.