The 1st Mounted Division was formed in August 1914 for the home defence of the United Kingdom. It was formed from existing mounted brigades of the Territorial Force, each of three regiments of Yeomanry. The Divisional order of battle would often change, as the First Line Brigades left for service overseas and were then replaced by Second Line units. It would be converted to the 1st Cyclist Division in July 1916, and was then broken up in November 1916 without being involved in active service. An unrelated 1st Mounted Division was formed in July 1916, from the 3rd Mounted Division, lasting until September 1917. Another incarnation of 1st Mounted Division was created in April 1918 from the Yeomanry Mounted Division, lasting until July 1918.