Under threat of invasion by the French Revolutionary government from 1793, and with insufficient military forces to repulse such an attack, the British government under William Pitt the Younger decided in 1794 to increase the Militia and to form corps of volunteers for the defence of the country.

[3] Despite the end of the Napoleonic Wars in 1815, the Yeomanry was retained by the government "for Military Service in aid of the Civil Power"[4] in the absence of organised police forces.

The last occasion was during the food riots in Devon in 1867 when 112 members of the 1st Devonshire Yeomanry Cavalry mustered in Exeter.

The Royal Warrant asked standing Yeomanry regiments to provide service companies of approximately 115 men each.

[10] On 17 April 1901, the regiment was renamed as the Royal 1st Devon Imperial Yeomanry and reorganised in four squadrons and a machine gun section.

On 1 April 1908, the regiment was renamed for the final time as the Royal 1st Devon Yeomanry and transferred to the Territorial Force, trained and equipped as hussars.

[16] At the outbreak of the First World War, the regiment was part of the 2nd South Western Mounted Brigade.

[17] Still with the 2nd South Western Mounted Brigade, in September 1915 the regiment left Colchester for Liverpool.

The regiment landed in Gallipoli on 9 October and was attached to the 11th (Northern) Division[18] (digging trenches).

In September 1915 it moved to Colchester, taking over the horses of the newly dismounted 1st Line regiment.

In March 1917 it resumed its identity as 2/1st Royal 1st Devon Yeomanry, still with the 2nd Cyclist Brigade, at Holt, Norfolk.

It remained in the Holt area until May 1918 when it went to Ireland with the 2nd Cyclist Brigade and was stationed at the Curragh and Mullingar until the end of the war.

Following the experience of the war, it was decided that only the fourteen most senior yeomanry regiments would be retained as horsed cavalry,[31] with the rest being transferred to other roles.