The 20th (Service) Battalion, The Durham Light Infantry was raised by the Sunderland Recruiting Committee in August 1915 and the early enlistments were sent to a tented camp in Wensleydale. As the weather closed in the battalion was moved to Barnard Castle, in County Durham. where it began training. The Battalion was allocated to the 41st Division, and as the only battalion in the division that had many miners in its ranks, it was well known for its digging ability. They joined the rest of the 41st Division in Aldershot and moved to France in May 1916. At the start of their overseas service the battalion spent much of their time in the trenches around Armentieres. They were not moved to the Somme front until the end of August and were in reserve during the successful assault at Flers. In late October they moved north to Ypres and stayed in the salient until June 1917 when they were part of the leading wave during The Battle of Messines, this was followed by actions at The Battles of the Menin Road and Polygon Wood.
Then in November they moved to the Italian Front where they spent four peaceful months with few casualties until they were rushed back to France to help stop the German advance in March 1918. They fought on until the end of the war and then joined the Army of Occupation in Cologne. When the order of battle was changed 20/Durham LI became the Divisional Pioneers of the Independent Division and was the last service battalion of the regiment to disband.