Infantry regiment (administrative)

The armies of some countries grouped their infantry battalions into regiments for administrative purposes but not for tactical purposes. The battalions of these regiments didn't all operate together: they could be in different brigades, divisions and theatres of war. Some battalions of each regiment stayed at home to train new recruits, who were sent out to other battalions when they were ready.

This description of The Royal Dublin Fusiliers in the First World War gives a sense of the range of places and engagements that different battalions in one regiment might have experienced:

"When the First World War began in August 1914, the 1st Battalion was in Madras. The 2nd Battalion was sent to France as part of the British Expeditionary Force. The 6th, 7th, 8th, 9th, 10th, and 11th Battalions were formed from the volunteers who enlisted after the outbreak of the war. The 1st, 6th and 7th were sent to Gallipoli, the 6th and 7th subsequently fighting at Salonika. The 1st and 2nd were at the opening of the Battle of the Somme. The 8th, 9th and 10th fought at Loos and later at the Somme in 1916. The 1st, 2nd, 8th, 9th and 10th were all involved in the 3rd Battle of Ypres, also known as Passchendaele. The 8th and 9th were merged and later disbanded, along with the 10th Battalion, in February 1918. The 1st and 2nd Battalions suffered heavily in the major German attack in March 1918. By the end of the Great War, 4,777 Royal Dublin Fusiliers had been killed."

For more information on this particular regiment, see Royal Dublin Fusiliers, UK.