The 55th Infantry Division was an infantry division of the British Army's Territorial Army (TA) that was formed in 1920 and existed through the Second World War, although it did not see combat. The division had originally been raised in 1908 as the West Lancashire Division, part of the British Army's Territorial Force (TF). It fought in the First World War, as the 55th Division, and demobilised following the fighting. In 1920, the 55th Division started to reform. It was stationed in the county of Lancashire throughout the 1920s and 1930s, and was under-funded and under-staffed. In the late 1930s, the division was reduced from three to two infantry brigades and gave up some artillery and other support units to become a motorised formation, the 55th Motor Division. This was part of a British Army doctrine change that was intended to increase battlefield mobility.

The Army Reserve is the active-duty volunteer reserve force of the British Army. It is separate from the Regular Reserve whose members are ex-Regular personnel who retain a statutory liability for service. The Army Reserve was known as the Territorial Force from 1908 to 1921, the Territorial Army (TA) from 1921 to 1967, the Territorial and Army Volunteer Reserve (TAVR) from 1967 to 1979, and again the Territorial Army (TA) from 1979 to 2014.