Battalions of the Regular Army
August 1914 : in Fyzabad, India. Returned to England, landing Plymouth on 16 November 1914.
Moved to Winchester and came under orders of 82nd Brigade in 27th Division.
20 December 1914 : landed at Le Havre.
Moved to Salonika, arriving 12 December 1915.
2 November 1916 : transferred to 29th Brigade in 10th (Irish) Division.
14 September 1917 : Division moved to Egypt for service in Palestine.
2 August 1919: cadre of the battalion arrives in England and is co-located with 2nd Battalion at Portsmouth.
24 October 1919: departs Tilbury for service in India.Lands at Bombay and proceeds to Madras, arriving 31 December 1919.
August 1914 : at Cork. Part of 17th Brigade in 6th Division. Moved to Cambridge on 18 August then on to Newmarket.
12 September 1914 : landed at St Nazaire.
14 October 1915 : transferred with Brigade to 24th Division.
19 October 1915 : transferred to 73rd Brigade in same Division.
1 February 1918 : moved to Tincourt and transferred to 47th Brigade in 16th (Irish) Division. Absorbed troops from disbanded 7th Bn.
13 April 1918 : absorbed troops from disbanded 6th Connaught Rangers.
23 April 1918 : transferred to 88th Brigade in 29th Division.
23 June 1919: battalion arrives in England and goes into barracks at Portsmouth.
4 November 1919: moves to Sobraon Barracks, Colchester. It subsequently served with the Army of Occupation in Upper Silesia.
The Leinster Regiment was disbanded on 22 August 1922.
3rd (Reserve) Battalion
August 1914 : at Birr. A depot/training unit, it moved on mobilisation to Cork, going on in November 1917 to Portsmouth as part of the Portsmouth garrison. Absorbed 4th and 5th Bns in May 1918.
4th (Extra Reserve) Battalion
August 1914 : at Maryborough. A depot/training unit, it moved on mobilisation to Crosshaven, going on in November 1914 to Passage West, May 1915 to Devonport. Moved in September 1915 to the Curragh, April 1916 to Limerick and August 1917 to Tralee. Moved to Dover in November 1917 and finally to Portsmouth in May 1918 where absorbed by 3rd Bn.
5th (Extra Reserve) Battalion
August 1914 : at Drogheda. A depot/training unit, it moved on mobilisation to Queenstown, going on in October 1914 to Passage West, May 1915 to Plymouth. Moved in September 1915 to Mullingar, April 1916 to the Curragh and June 1917 to Laytown, August 1917 to Boyle and next month to Birr. Moved to Glencorse in November 1917 and finally to Portsmouth in May 1918 where absorbed by 3rd Bn.
Battalions of the Territorial Force
As the Territorial and Reserve Forces Act of 1907 did not call for the creation of TF units in Ireland, the regiment had no TF battalions.
Battalions of the New Armies
6th (Service) Battalion
Formed at Dublin in August 1914 as part of K1 and came under command of 29th Brigade in 10th (Irish) Division. Moved to Fermoy, quickly on to the Curragh and by October was at Birr but back to the Curragh in February 1915.
May 1915 : moved to Basingstoke.
9 July 1915: embarked at Liverpool and sailed to Gallipoli via Mudros. Landed Anzac Cove 5 August 1915.
29 September 1915 : moved via Mudros to Salonika.
14 September 1917 : moved to Egypt for service in Palestine.
May 1918 : left the Division and sailed from Port Said, arriving Marseilles 1 June.
23 July 1918 : came briefly under command of 14th (Light) Division and then 34th Division.
20 July 1918 : placed under command of 198th Brigade in 66th (2nd East Lancashire) Division.
12 September 1918 : disbanded at Abancourt.
7th (Service) Battalion
Formed at Fermoy in October 1914 as part of K2 and came under command of 47th Brigade in 16th (Irish) Division. Moved to Kilworth in January 1915. Moved to England in September 1915, going to Blackdown.
18 December 1915 : landed at Le Havre.
14 February 1918 : disbanded at Tincourt, troops going to 2nd Leinster and 19th Entrenching Battalion.