In addition to their two Regular battalions, the Leinster Regment raised a number of Service and home based Reserve battalions:
Total - 7:
Regular - 2. Service - 2. Reserve - 3.
At the outbreak of war, they were based at Fyzabad in India, and joined 82nd Brigade, 27th Division, and arrived in France during December 1914.
After spending a year on the Western Front, they moved with the Division to Salonika on 12 December 1915.
After a year there, the battalion transferred to 29th Brigade, 10th (Irish) Division in September 1916 and moved with the division to Palestine in September 1917, where they remained until the end of the war.
At the outbreak of war, they were based in Ireland and, as part of 17th Brigade, 6th Division, arrived in France in September 1914.
They transferred to 73rd Brigade, 24th Division during October 1915 and, after over two years on the Western Front, they transferred to 47th Brigade, 16th (Irish) Division in Feburary 1918. At this time, they absorbed troops from the disbanded 7th Bttn and soon after, more men came in from the disbanded 6th Bttn, Connaught Rangers.
In April 1918, they transferred to 88th Brigade, 29th Division.
Formed in August 1914, they joined 29th Brigade, 10th (Irish) Division and sailed to Gallipoli July 1915 and landed at Anzac Cove in August 1915.
They moved with the division to Salonika in September 1915 and, after two years on that front, moved to Palestine in September 1917.
In May 1918, the battalion left 10th (Irish) Division and were placed under command of 198th Brigade, 66th (2nd East Lancashire) Division before being disbanded in September 1918.
Formed in October 1914 they joined 47th Brigade, 16th (Irish) Division, landing in France during December 1915.
They served throughout the division's campaigns before being disbanded in April 1918, with their men going to both 2nd Leinsters and 19th Entrenching Battalion.
The Victoria Cross was awarded to four men, who were serving with the Leinster Regiment during the First World War:
2,176 men from the Leinster Regiment are listed in the CWGC database of First World War deaths: