However, on the outbreak of war on 4 August 1914, many members volunteered for Imperial Service.

Therefore, TF units were split in August and September 1914 into 1st Line (liable for overseas service) and 2nd Line (home service for those unable or unwilling to serve overseas) units.

[2] The Scottish Horse was initially expanded by the formation of a 3rd Regiment in August 1914.

They moved to Kettering, Northamptonshire and formed 2/1st Scottish Horse Mounted Brigade.

[3] At the end of 1917, the brigade moved to Fife with the regiments at Ladybank (2/1st), St Andrews (2/2nd) and Cupar (2/3rd).