1915.
Artois.
1. In March, 1915, the 120th Reserve Infantry Regiment was given to the 58th Division, a new formation.
2. In May, 1915, elements of the 26th Reserve Division were sent to Artois on detached service and fought at Neuville-St. Vaast. In June some units of the 99th Reserve Regiment (3d and 4th Battalions) and the 180th Infantry Regiment took part in the battles around Arras (Le Labyrinthe).
Somme.
3. At the beginning of July these elements rejoined the division, which continued to hold the Somme sector before Bapaume.
1916.
Somme.
1. On July 1, 1916, the 26th Reserve Division withstood the Franco-British offensive north and south of the Ancre (Beaumont Hamel, Ovillers, Thiepval). (The total of the losses on the Somme amounted to 10,042 men.) The 99th Reserve Infantry Regiment lost 48 officers and 2,070 men. (Official List of Casualties.)