The South Irish Horse existed for a mere 20 years, formed in 1902 as the South of Ireland Imperial Yeomanry and disbanded in July 1922 along with five other famous Irish Regiments;
{The Royal Irish Regiment, The Connaught Rangers, The Leinster Regiment, The Royal Munster Fusiliers and The Royal Dublin Fusiliers}. Raised as The South of Ireland Imperial Yeomanry in 1902, it can trace its roots to various companies of Imperial Yeomanry. The 61st (South Irish) Company, 17th Battalion, Imperial Yeomanry being the most obvious. This company was raised on the 7th March 1900.

  During the Boer War many men enlisted to fight in South Africa. Their reasons ranged form patriotic fervour a desire for adventure or just the rather enticing rates of pay. Rather than enlist with Regular Army regiments many men joined existing local organisations, including the various Yeomanry regiments. The Yeomanry had been raised as a local force for service at home, and so, by tradition and Act of Parliament they could not serve overseas. A solution to this dilemma was found by raising the Imperial Yeomanry. Recruits were drawn from existing Yeomanry regiments, reserves and volunteers. Men enlisted for a period of one year, like many wars it wasn't supposed to last quite so long.
The table below is a breakdown of Imperial Yeomanry Companies with affiliation to Ireland.

On 7th January 1902 the South of Ireland Imperial Yeomanry regiment was raised along with a sister regiment, the North of Ireland Imperial Yeomanry. Initially headquatered at Artillery Barracks in Limerick it had one squadron there, one in Cork and two in Dublin. . To see transcribed lists of men who were in the South of Ireland Imperial Yeomanry, taken from their club gazette, follow these links. Officers and Permanent staff,  HQ & the Band, A Squadron, B Squadron, C Squadron and finally D Squadron. In 1906 the regiment provided an escort, commanded by 2nd Lieutant Lynol Loyd Hewson, for the King and Queen in Waterford
  

The Haldane reforms of 1908 reorganised the British Army entirely. Yeomanry regiments now became part of the Territorial Force. This legislation did not apply in Ireland. As a result the North and South Irish Imperial Yeomanry were re-designated as Special Reserve cavalry regiments. It was renamed as the South Irish Horse from 7th July 1908. A party of 25 men attended the coronation of King George V in 1911.

The declaration of war against Germany in August 1914 found the South Irish Horse at summer camp, as was its sister regiment the North Irish Horse. Together they supplied a composite regiment who acted as GHQ (General Head Quarters) troops in the BEF (British Expeditionary Force) in France, B Squadron from the South Irish Horse and two from the North Irish Horse.

Briefly, the regiment served as separate divisional cavalry squadrons and then as 2 corps cavalry regiments. In September 1917 the officers and men of both regiments were retrained as infantry and formed 7th (South Irish Horse) Battalion Royal Irish Regiment. The battalion was posted to 49th Infantry Brigade in 16th (Irish) Division. A look at the list of war dead will show 21 men recorded as Killed in Action on 12th December 1917 and a further 9 Died of Wounds by the end of the month. All of these men had previously been in the South Irish Horse. In Terance Denman's book "Ireland's Unknown Soldiers", he states that actually 22 men were killed and over 40 wounded by one artillery shell at St Emilie on 13th December 1917 and not on the 12th. It is understandable for the official record to be occasionally incorrect, especially when considering it records over 700 000 dead from the British Isles alone.

On 21st March 1918 the battalion was caught in the maelstrom of the German Kaiserschlacht (Kaiser's Battle) offensive. The Official History records that, "2 Coys of 7/Royal Irish posted in forward zone suffered terribly; not a man succeeded in escaping." 77 officers and men of 7th (SIH) Royal Irish Regiment were killed in action that day, 42 were formerly South Irish Horse. 14 officers of the battalion were captured that day 6 of whom were formerly South Irish Horse. By the end of the month over 90 men of the battalion were dead or dying. According to the War Diary of 49th Infantry Brigade the battalion strength on 30th March 1918 was 1 officer and 34 other ranks. The battalion strength on 20th March is not known but a sister battalion (2nd Royal Irish Regiment) in the brigade had a strength of 18 officers and 514 men before the battle and 1 officer and 31 other ranks on 30th March. 15 officers of this battalion were also captured (two of whom were also formerly South Irish Horse). Far more details can be found in "Orange Green and Khaki" by Tom Johnstone.

In April 1918 the battalion was reduced to a cadre and reformed in June with 835 men from other regiments. It retained South Irish Horse in its title but must have had very few former members in its numbers. In the battalion  from April until the end of the war one man was killed in action and two died of wounds who were previously South Irish Horse and 16 former South Irish Horse died. For a simple analysis of men died in the 7th follow this link. For a list of the war dead see this page.

Using printed Army lists I have managed to identify over 150 officers, to see a list of these men, who are from both the SIY and SIH follow this link. A further list containing names of other ranks as well as officers from various sources click here. The 1914 Star medal roll for the SIH was used to produce the list on this page. First of five pages for the 1914-1915 Star medal roll can be seen here. Follow the link to see information taken from the London Gazette which is of relevance to the SIH.

More details of the history of the regiment during World War I follow.

The following information is taken from;
"BRITISH REGIMENTS 1914-1918" by Brigadier E.A. James

Naval and Military Press. 5^th Edition April 1998. Part I, page 15

SOUTH IRISH HORSE
‘France and Flanders, 1915-18’

4.8.14 Dublin: attached to 3^rd Cavalry Brigade. On mobilisation the regiment was split up and the squadrons were employed mainly as divisional cavalry until 1916. After this as corps cavalry and after September 1917 as infantry. Three new squadrons were formed.

‘A’ Squadron joined 21^st Division at Aldershot in 1915 as divisional cavalry. 12.9.15 landed at Le Havre. 11.5.16 to XV Corps Cavalry Regiment. November 1916 to IX Corps Cavalry Regiment. 16.1.17 to XVIII Corps Cavalry Regiment.

‘B’ (later ‘S’) Squadron went to France on 17.8.14 as GHQ Troops. 14.5.15 to 2^nd Division as Divisional Cavalry. 15.5.16 to I Corps Cavalry Regiment and became ‘S’ Squadron.

‘C’ Squadron joined 16^th (Irish) Division at Aldershot in 1915 as Divisional Cavalry. 16.12.15 to France. 17.5.16 to I Corps Cavalry Regiment.

‘E’ Squadron landed at Havre and joined 39^th Division as Divisional Cavalry on 17.3.16. 17.5.16 to I Corps Cavalry Regiment.

‘F’ Squadron landed in France from Ireland on 18.5.17 and on 27.5.17 replaced ‘B’ Squadron 1/1^st Hertfordshire Yeomanry in XVIII Corps Cavalry Regiment.

‘S’ (later ‘B’) Squadron joined 32^nd Division on Salisbury Plain in 1915 as Divisional Cavalry. 25.11.15 landed at Havre. 14.5.16 to XV Corps Cavalry Regiment and became ‘B’ Squadron. 21.11.16 to IX Corps Cavalry Regiment. January 1917 to XVIII Corps Cavalry Regiment.

On 17.5.16 ‘C’, ‘E’ and ‘S’ Squadrons formed I Corps Cavalry Regiment and were known as the 1^st South Irish Horse. It left I Corps in August 1917, was dismounted and went to Etaples. At the end of August it amalgamated with the 2^nd South Irish Horse and on 1.9.17 formed the 7^th (South Irish Horse) Battalion, Royal Irish Regiment. 14.10.17 to 49^th Brigade 16^th (Irish) Division. 18.4.18 reduced to cadre. End of June reformed and on 4.7.18 to 21^st Brigade 30^th Division until the end of the war.

On 11 and 14.5.16 ‘A’ and ‘S’ Squadrons went to XV Corps as Corps Cavalry when ‘S’ Squadron became ‘B’. On 21.5.16 RHQ and ‘D’ Squadron Wiltshire Yeomanry joined XV Corps Cavalry Regiment. November 1916 the two South Irish Horse Squadrons joined ‘C’ Squadron Hampshire Yeomanry in IX Corps Cavalry Regiment. January 1917 ‘A’ and ‘B’ Squadrons with ‘B’ Squadron 1/1^st Hertfordshire Yeomanry formed XVIII Corps Cavalry Regiment. May 1917 ‘F’ Squadron from Ireland joined in place of ‘B’ Hertfordshire Yeomanry. In August 1917 2^nd South Irish Horse were dismounted and went to Etaples. Joined 1^st South Irish Horse and formed 7^th (South Irish Horse) Battalion, Royal Irish Regiment.(See above).

A reserve regiment was formed and remained in Ireland for the war, most of the time stationed at Cahir, in Tipperary.
Part II, page 61                               THE ROYAL IRISH REGIMENT
                                                           7^th (South Irish Horse) Battalion

Formed in France on 1.9.17 from the dismounted 1^st and 2^nd South Irish Horse. The two regiments had been the Corps Cavalry Regiments of I and XVIII Corps and were dismounted in August 1917 for training as infantry. 14.10.17 to 49^th Brigade 16^th (Irish) Division at Ervillers. 18.4.18 reduced to cadre. 26.6.18 reformed with 500 all ranks from Royal Dublin Fusiliers, 250 from Royal Munster Fusiliers and 85 from Royal Irish Regiment. 4.7.18 to 21^st Brigade 30^th Division at Hellbroucq. 11.11.18 21^st Brigade 30^th Division Belgium; Elleselles, east of Renaix.

The table following table was drawn up from the above information and hopefully simplifies it!

Battle Honours of The South Irish Horse 1914-1922

Loos - Somme, 1916, 1918 - Albert, 1916 - St Quentin - Rosières - Avre -
Ypres, 1918 - Courtai - France and Flanders, 1915-18.

To see transcriptions of the units War Diaries please use the link and to see a list of men who are mentioned in the diaries along with many others click here.

The following information is taken from;

"CAVALRY AND YEOMANRY BADGES OF THE BRITISH ARMY 1914" by F. Wilkinson.
Arms and Armour Press.  1973.

Page 49.  BADGES.        Plate 238 – pre 1908.  Both of brass with ring attachments.

Shamrock flat with raised rim, letters SIY, bottom left, center and bottom right in that order.

.The picture above came from the 16th Division web page linked above

Special Reserve         South Irish Horse:

Uniform – green.   Facings – red and green.      Station – Beggars Bush Barracks, Dublin
To see three black and white photographs of the uniform follow these links.
One on horse back second also on horse back third on foot

To see more pictures follow the link.

       Sources;
The Public Record Office at Kew
Soldiers Died In The Great War. HMSO 1922. Parts 1 and 23
Officers Died in the Great War 1914-1919. Pub. by J B Hayward and Son 1988
Orange Green and Khaki. Tom Johnstone. Gill and Macmillan. 1992
List of British Officers taken prisoner August 1914- November 1918.
Boer Wars (2) 1898-1902, Men at Arms Series no. 303 by Ian Knight and Gerry Embleton.
Yeomanry Wars by Peter D Athaws. Scottish Cultural Press. Ó 1994.
Military Operations-France and Belgium1914-1918, 16 vols. London: HMSO 1922-49. By Brigadier-General Sir James Edmonds. 1918 Volume One, The German March Offensive and its Preliminaries.
The Irish Regiments: a Pictoral History, 1683-1987. R.G. Harris. 1989
The Irish Sword. Vol XIII. The Journal of the Military History Society of Ireland.
Lineage book of British Land Forces 1660-1978 Vol I. J.B.M. Frederick 1984
Cavalry & Yeomanry Badges of The British Army 1914 by F. Wilkinson. Arms & Armour Press
16th Irish Division: Battalions, Support Units and Dates, page maintained by SHK
16th Irish Division  page maintained by SHK
Copies of the London Gazette, HMSO London, various dates, 1914 - 1919
Printed British Army lists, both Harts and the official printed lists, various dates, 1900 - 1922

Further reading;
Ireland's Unknown Soldiers by Terence Denman, Irish Academic Press
For more information on The Royal Munster Fusiliers  follow the link