In late 1914, when the 3rd (Special Reserve) Battalion was overflowing with recruits, permission was given to raise from it a second reserve battalion. The 11th was formed from a nucleus of the 3rd Devons and quickly achieved full strength. Based at Wareham, it acted as a holding and training unit, supplying the Devon battalions in battle – especially the 8th and 9th – with reinforcements.
In August 1916 its connections with the Devonshire Regiment were severed and it became part of the new Training Reserve, which supplied reinforcements to all infantry units.