The British cavalry were the first British Army units to see action during the First World War. Captain Hornby of the 4th Dragoon Guards is reputed to have been the first British soldier to kill a German soldier, using his sword, and Corporal Edward Thomas of the same regiment is reputed to have fired the first British shot shortly after 06:30 on 22 August 1914, near the Belgian village of Casteau. The following Battle of Mons was the first engagement fought by British soldiers in Western Europe since the Battle of Waterloo, ninety-nine years earlier. In the first year of the war in France, nine cavalry brigades were formed for three British cavalry divisions. Other regiments served in six brigades of the two British Indian Army cavalry divisions that were formed for service on the Western Front. Three regiments also fought in the campaign in Mesopotamia, the only other theatre of the First World War where British cavalry served.

The 4th Royal Irish Dragoon Guards was a cavalry regiment in the British Army, first raised in 1685 as the Earl of Arran's Regiment of Cuirassiers. It was renamed as the 4th Dragoon Guards in 1788 and service for two centuries, including the First World War, before being amalgamated with 7th Dragoon Guards, to form the 4th/7th Dragoon Guards in 1922.