The Territorial Force, as formed in 1908, had 54 cavalry regiments organised in 14 brigades and known collectively as the Yeomanry. This meant that the Yeomanry consisted of 1,168 officers and 23,049 other ranks in September 1913 out of a Territorial Force which numbered 9,390 officers and 236,389 other ranks.

This is a massive figure when we consider the modest increases in the size of the current Territorial Army under the 2020 reforms. The failure to extend the Territorial Force to Ireland meant that two other auxiliary cavalry regiments, the North Irish Horse and South Irish Horse, were formed as units of the Special Reserve. This meant that, unlike Yeomanry regiments proper, they had a longer summer camp and undertook to serve overseas in the event of war. Indeed, it was squadrons of the North and South Irish Horse which were the first non-regular units of the British army to serve overseas in the First World War, forming part of the original British Expeditionary Force. Of the 54 Yeomanry Regiments only the men of the Northumberland Hussars had undertaken the Imperial Service Obligation committing themselves to overseas service in the event of war...