In August 1918 it was renumbered as 101st (Bucks. & Berks. Battalion, Machine Gun Corps. They remained on the Western Front for the rest of the war. At the Armistice, it was serving as Army Troops with the Second Army. The 2nd Line regiment was formed at Buckingham in September 1914. By March 1915 it was with 2/2nd South Midland Mounted Brigade in 2/2nd Mounted Division and was at King's Lynn in Norfolk. On 31 March 1916 the remaining Mounted Brigades were ordered to be numbered in a single sequence and the brigade became the 11th Mounted Brigade (and the division 3rd Mounted Division). In July 1916 there was a major reorganization of 2nd Line yeomanry units in the United Kingdom. All but 12 regiments were converted to cyclists; the 2/1st Royal Buckinghamshire Yeomanry remained mounted and transferred to the 1st Mounted Brigade in the new 1st Mounted Division (3rd Mounted Division redesignated) at Brentwood. In March 1917 it moved to Much Hadham and in April back to Brentwood. In August 1917 the regiment was converted to a cyclist unit in 11th Cyclist Brigade, The Cyclist Division and was stationed at Canterbury. There were no further changes before the end of the war. The 3rd Line regiment was formed in 1915; in the summer it was affiliated to the 7th Reserve Cavalry Regiment at Tidworth. Early in 1917 it was absorbed into the 3rd Reserve Cavalry Regiment at Aldershot. On 7 February 1920 the Regiment was reconstituted in the Territorial Army with HQ still at Aylesbury. Following the experience of the war, it was decided that only the 14 most senior yeomanry regiments would be retained as horsed cavalry, with the rest being transferred to other roles. As a result on 29 April 1921 the Regiment was amalgamated with the Berkshire Yeomanry and simultaneously transferred to the Royal Artillery to form 99th (Buckinghamshire and Berkshire) Brigade, RFA with HQ at Aylesbury. The two yeomanry regiments retained their own identities and badges within the amalgamated unit, with each providing two batteries. The Buckinghamshire Yeomanry formed 393 (Royal Bucks Yeomanry) Battery at Aylesbury and 394 (Royal Bucks Yeomanry) Battery at High Wycombe. The brigade / regiment underwent a number of redesignations before the outbreak of the Second World War.