It started the war as a member of the 3rd Cavalry Brigade, 1st Cavalry Division. The 3rd Cavalry Brigade was transferred to the 2nd Cavalry Division on 13 September 1914.
As a unit of the 3rd Cavalry Brigade, 1st Cavalry Division, it will have taken part in the following battles and engagements.
|The Cavalry Division had no permanent existence before the outbreak of War. The units of which it was composed on mobilization were quartered at various stations in England and Ireland, viz:- the 1st Cav. Bde., VII. Bde., R.H.A., 1st Field Sqd., R.E., 1st Signal Squadron, and No. 1 Signal Troop, at Aldershot; the 2nd Cav. Bde. and No. 2 Signal Troop, at Tidworth; the 3rd Cav. Bde., II. Bde., R.H.A., 4th Field Troop, 4th Cav. Bde., and No. 4 Signal Troop, were stationed at Canterbury, Shorncliffe, and London. The division crossed to France between the 15th and 18th August, concentrated to the East and South-east of Mauberge between the 18th and 20th August, and began to move forward on the 21st.Throughout the War the 1st Cavalry Division served on the Western Front in France and Belgium, and was engaged in the following operations:-|
|23 and 24 August||Battle of Mons.|
|24 to 05 September||RETREAT FROM MONS.|
|26 August||Battle of le Cateau [under II. Corps].|
|06 to 09 September||Battle of the Marne.|
As a unit of the 3rd Cavalry Brigade, 2nd Cavalry Division, it will have taken part in the following battles and engagements.
|12 to 15 September||BATTLE OF THE AISNE|
|12 October to 02 November||Battle of Messine [Cav. Corps].|
|13 to 17 October||Battle of Armentieres (3rd and 4th Cav. Bdes.) [Cav. Corps].|
|BATTLES OF YPRES|
|30 and 31 October||Battle of Gheluvelt (3rd Cav. Bde. and part of 4th and 5th Cav. Bdes.) [I. Corps].|
|BATTLES OF YPRES|
|26 April to 03 May||Battle of St. Julien [Plumer’s Force, Second Army].|
|24 and 25 May||Battle of Bellewaarde Ridge [V. Corps, Second Army].|
The MG Section was brigaded into the 3rd Cavalry MG Squadron on 29 February 1916.
In 1922, the Machine Gun Corps was disbanded and the 5th Lancers were merged with the 16th Lancers to form the 16th/5th Lancers.