4th Ersatz Division ( German Empire ) The 4th Ersatz Division ( " 4 . Ersatz - Division " ) was a unit of the German Army , in World War I . The division was formed on mobilization of the German Army in August 1914 . The division was disbanded in 1919 , during the demobilization of the German Army after World War I . Formation and recruitment . The 4th Ersatz Division was formed on mobilization from 13 brigade replacement battalions ( " Brigade - Ersatz - Bataillone " ) . Each brigade replacement battalion was numbered after its parent infantry brigade , and was formed with two companies taken from the replacement battalion of each of the brigade ' s two infantry regiments . Thus , collectively , the 13 brigade replacement battalions represented troop contributions from 26 different infantry regiments . The four battalions of the 9th Mixed Ersatz Brigade were from the Prussian Province of Brandenburg , as were the brigade ' s artillery , cavalry and pioneer formations . Two battalions of the 13th Mixed Ersatz Brigade were from the Prussian Province of Saxony , one was a mixed battalion from Prussian Saxony and the Duchy of Anhalt , and one was a mixed battalion from Prussian Saxony and the Duchy of Saxe - Altenburg . The brigade ' s artillery , cavalry and pioneer formations were primarily from Prussian Saxony . The five battalions of the 33rd Mixed Ersatz Brigade , from the IX Army Corps area in northern Germany , were even more mixed : the 33rd Brigade Replacement Battalion was from the Hanseatic Cities of Bremen and Hamburg ; the 34th from the Grand Duchies of Mecklenburg - Schwerin and Mecklenburg - Strelitz ; the 35th and 36th from Schleswig - Holstein ; and the 81st from Schleswig - Holstein and the Hanseatic City of Lübeck . The brigade ' s artillery , cavalry and pioneer formations were mainly from Schleswig - Holstein , Mecklenburg - Schwerin and Hamburg . Combat chronicle . The 4th Ersatz Division initially fought on the Western Front in World War I . It fought in the Battle of the Frontiers , seeing action in Lorraine and against the French defensive line from Nancy to Epinal . At the end of September 1914 , the division was transferred from Lorraine to Belgium , where it participated in the Siege of Antwerp . After Antwerp fell , the division occupied the city and participated in follow - on fighting in Belgian Flanders . It fought in the Battle of the Yser and then went into the line on the Yser until November 1916 . During this period , the division fought in the Second Battle of Ypres in April / May 1915 and in the Battle of the Somme in October 1916 . It was in the trenchlines in the Somme region from December 1916 to February 1917 . After fighting before the German Siegfried position , the division participated in the Battle of Arras . In late May 1917 , the division was transferred to the Eastern Front . In July , it resisted the Russian Kerensky Offensive , and then participated in follow - on fighting in eastern Galicia . In December 1917 , the division returned to the Western Front . It was in the trenchlines in Flanders and the Artois until April 1918 , when it fought in the Battle of Armentières , part of the Battle of the Lys , also known as the German Lys Offensive or the Fourth Battle of Ypres . The division later fought in the Second Battle of the Marne . Allied intelligence considered the division a fairly good division in 1917 , but rated it third class in 1918 , noting that it had not distinguished itself in the battles of 1918 . Order of battle on mobilization . The order of battle of the 4th Ersatz Division on mobilization was as follows : Order of battle on July 15 , 1915 . The division was restructured in the summer of 1915 . The 33rd Ersatz Brigade was dissolved in July 1915 . The other mixed Ersatz brigades were converted to Ersatz infantry brigades as cavalry , artillery , and pioneer Ersatz units were grouped and reorganized . The brigade replacement battalions were grouped into infantry regiments . The order of battle on July 15 , 1915 was as follows : Order of battle on March 1 , 1918 . The division underwent more structural changes as the war progressed . The 4th Ersatz Division was triangularized in September 1916 . The 359th Infantry regiment was transferred to the newly formed 206th Infantry Division in August 1916 . Over the course of the war , cavalry was reduced , pioneers were increased to a full battalion , and an artillery command and a divisional signals command were created . The division ' s order of battle on March 1 , 1918 was as follows :