1/1st
August 1914 : in Edinburgh. Part of the Lowland Mounted Brigade.
Summer 1915 : split up as follows:- RHQ and B Squadron joined 25th Division; in May 1916 it moved to become V Corps Cavalry Regiment; in JUly 1917 it dismounted and went for infantry training; in September 1917 the men joined the 17th Bn, the Royal Scots. A Squadron went to 26th Division; in November 1916 it joined 8th Mounted Brigade, and in May 1917 moved to become XII Corps Cavalry Regiment. D Squadron joined 22nd Division; in November 1916 it joined 8th Mounted Brigade, and in May 1917 moved to become XII Corps Cavalry Regiment.
11 May 1917: A and D Squadrons formed XII Corps Cavalry Regiment in Salonika, where it then remained.
2/1st
Formed September 1914, attached to 2/1st Lowland Mounted Brigade.
Remained in Scotland until moving to Ireland in May 1918, where it then remained. Converted into a cyclist unit in July 1916.
3/1st
Formed in 1915. Remained in United Kingdom until absorbed by 4th Reserve Cavalry Regiment in early 1917.