Of the three battalions, only the 1st Royal Irish Fusiliers had seen active service, fighting in the Battle of France where they were forced to retreat to Dunkirk and were subsequently evacuated to England.

In March 1943, it exchanged with the 1st Guards Brigade and joined the 78th Battleaxe Infantry Division and fought with distinction throughout the rest of the Tunisian Campaign.

In late April, the 38th (Irish) Brigade played a lead role in the capture of the German defensive positions in the mountains north of Medjez-el-Bab and the campaign ended in mid-May, with almost 250,000 Axis soldiers surrendering.

[3] After a short rest, the brigade again saw action in the Allied invasion of Sicily (in particular the capture of Centuripe), and in the Italian Campaign, spearheading the British Eighth Army's advance to the Volturno Line, and later at the Battle of Monte Cassino and at Lake Trasimene.

During May 1945, it was (briefly) detached to both 46th Infantry and 6th Armoured Divisions and the brigade then was allotted occupation duties in Carinthia in southern Austria, before being formally disbanded in April 1947.