The Sussex Imperial Yeomanry was formed 14 June 1901, as one of the Imperial Yeomanry regiments created to serve in the Second Anglo-Boer War in South-Africa. The Imperial Yeomanry regiments were disbanded in 1908.
In accordance with the Territorial and Reserve Forces Act 1907 (7 Edw. 7, c.9) which brought the Territorial Force into being, the TF was intended to be a home defence force for service during wartime and members could not be compelled to serve outside the country. 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. Later, a 3rd Line was formed to act as a reserve, providing trained replacements for the 1st and 2nd Line regiments.
The 1st Line regiment was mobilised on 4 August 1914 at the outbreak of the First World War and was in the Canterbury area (under Second Army of Central Force) until September 1915. It was dismounted and left Kent for Liverpool; on 24 September it boarded RMS Olympic and sailed the next day. It arrived at Lemnos on 1 October. The regiment landed in Gallipoli on 8 October and was attached to the 42nd (East Lancashire) Division. Within days of the landing the Regiment reported many men suffering from enteritis. While at Gallipoli they spent time in the trenches at Border Barricade and Fusilier Bluff. On 30 December it was evacuated to Mudros with 42nd Division; it left the Division at Mudros on 2 January 1916.
The brigade, with the regiment, was withdrawn to Egypt in February 1916 and formed part of the Suez Canal Defences. On 22 February, South Eastern Mounted Brigade was absorbed into the 3rd Dismounted Brigade (along with the Eastern Mounted Brigade). The brigade served as part of the Suez Canal Defences from 14 March to 26 July attached to 42nd (East Lancashire) Division; it then joined the Western Frontier Force. By the end of the year, it was back on the Suez.
The brigade was with the Suez Canal Defences when, on 14 January 1917, Egyptian Expeditionary Force (EEF) Order No. 26 instructed that the 2nd, 3rd and 4th Dismounted Brigades be reorganized as the 229th, 230th and 231st Brigades. The brigade units were reorganized in January and February 1917. As a result, the 1/1st Sussex Yeomanry was converted to infantry at Mersa Matruh on 3 January 1917 and redesignated 16th (Sussex Yeomanry) Battalion, Royal Sussex Regiment.
On 23 February, the GOC EEF (Lt-Gen Sir A.J. Murray) sought permission from the War Office to form the 229th, 230th and 231st Brigades into a new division. The War Office granted permission and the new 74th (Yeomanry) Division started to form. The 230th Brigade joined the division at Deir el Balah between 9 and 13 April. The battalion remained with 230th Brigade in 74th (Yeomanry) Division for the rest of the war.
With the 74th Division, the battalion took part in the invasion of Palestine in 1917 and 1918. It fought in the Second and Third Battles of Gaza (including the capture of Beersheba and the Sheria Position). At the end of 1917, it took part in the capture and defence of Jerusalem and in March 1918 in the Battle of Tell 'Asur. On 3 April 1918, the Division was warned that it would move to France and by 30 April 1918 had completed embarkation at Alexandria.
In May 1918, the battalion landed at Marseilles, France with 74th (Yeomanry) Division. It served in France and Flanders with the division for the rest of the war. By 18 May, the division had concentrated around Rue in the Abbeville area. Here the dismounted Yeomanry underwent training for service on the Western Front, particularly gas defence.
On 14 July 1918 the Yeomanry Division went into the line for the first time, near Merville on the right of XI Corps. From September 1918, as part of III Corps of Fourth Army, it took part in the Hundred Days Offensive including the Second Battle of the Somme (Second Battle of Bapaume) and the Battles of the Hindenburg Line (Battle of Épehy). In October and November 1918 it took part in the Final Advance in Artois and Flanders. By the Armistice it was near Tournai, Belgium, still with 74th (Yeomanry) Division.
With the end of the war, the troops of 74th Division were engaged in railway repair work and education was undertaken while demobilisation began. The division and its subformations were disbanded on 10 July 1919.
The 2nd Line regiment was formed at Brighton in September 1914 and remained there until May 1915. It then moved to Maresfield and joined 2/1st South Eastern Mounted Brigade; there it took over the horses of 2nd King Edward's Horse who were going dismounted to the Western Front. In October 1915 the regiment was at Canterbury. On 31 March 1916, the remaining Mounted Brigades were ordered to be numbered in a single sequence; the brigade was numbered as 14th Mounted Brigade and joined 4th Mounted Division.
In July 1916, 4th Mounted Division became 2nd Cyclist Division and the regiment was converted to a cyclist unit in 5th Cyclist Brigade at Great Bentley. In November 1916 the division was broken up and the regiment was merged with the 2/1st Surrey Yeomanry to form 8th (Surrey and Sussex) Yeomanry Cyclist Regiment in 3rd Cyclist Brigade at Ipswich. In March 1917 it resumed its identity as 2/1st Sussex Yeomanry at Ipswich, and later moved to the Woodbridge area. In April 1918, the regiment moved with 3rd Cyclist Brigade to Ireland, landing in Dublin on 21 April. Initially it was stationed at Clandeboye and in September 1918 to Boyle; there was no further change before the end of the war.
The 3rd Line regiment was formed in July 1915 at Brighton and affiliated to the 3rd Reserve Cavalry Regiment at Canterbury. In the summer of 1916 it was dismounted and attached to the 3rd Line Groups of the Home Counties Division at Crowborough as its 1st Line was serving as infantry. The regiment was disbanded in January 1917 with personnel transferring to the 2nd Line regiment or to the 4th (Reserve) Battalion of the Royal Sussex Regiment at Tunbridge Wells.
On reforming the Territorial Army, the 14 senior Yeomanry regiments remained horsed cavalry regiments (6 forming the 5th and 6th Cavalry Brigades) while the remaining Yeomanry Regiments were reassigned as artillery. In 1922 the Sussex Yeomanry was amalgamated with the Surrey Yeomanry and reformed as the 98th (Surrey and Sussex Yeomanry) Brigade, Royal Field Artillery.
During the Second World War there were two regiments associated with the Sussex Yeomanry
98th (Surrey & Sussex Yeomanry Queen Mary's) Field Regiment, Royal Artillery
144th (Surrey & Sussex Yeomanry Queen Mary's) Field Regiment, Royal Artillery
They took part in the Battle of France and the campaigns in East Africa, North Africa and Italy.
In 1947 the Regiment was reformed as a separate Regiment. This reformation lasted until April 1, 1967 when they were once again amalgamated with other Yeomanry Regiments to become the 100th (Eastern) Medium Regiment, Royal Artillery (Volunteers).
They were again redesignated as the 100th (Yeomanry) Regiment Royal Artillery (Volunteers) in September 1976. In April 1993 200 Battery was converted to 127 (Sussex Yeomanry) Field Squadron 78 (Fortress) Engineer Regiment Royal Engineers in support of 3rd UK Division. The 78 (Fortress) Engineer Regiment was disbanded on 1 July 1999 as a result of the Options for Change restructuring programme.
The title Sussex Yeomanry continues in use as the designation of one troop of 579 Field Squadron (EOD). Part of 101 (London) Engineer Regiment (Explosive Ordnance Disposal) (Volunteers), 1 (Sussex Yeomanry) Field Troop is based at Brighton TA centre.
Honorary ColonelsWilliam Nevill, 1st Marquess of Abergavenny 28 September 1901 - ?