During the opening months of the War, the Brigade had its full share of fighting and saw action at Mons, Le Cateau, at the crossings of the Marne and Aisne and in the first battles in Flanders.

Hill 60 was the highest point on what was known as the "Caterpillar Ridge" and as such was an excellent post for observation of the ground area around Zillebeke and Ypres.

The Germans, unable to obtain victory, eventually resorted to the use of chlorine gas and Brigade casualties during the first week in May 1915 were 33 officers and 1,553 men.

When the 5th Division was sent to France late 1939, the 15th Brigade was sent instead in May to Norway, as part of Sickleforce to participate in the unsuccessful Norwegian Campaign, under the command of Lieutenant-General H.R.S.Massey.

The Brigade served with this formation for the rest of the war, seeing action in the Allied invasion of Sicily in July 1943 and Italian Campaign later in the year.

After participating in the later stages of the Battle of Anzio, the brigade was deployed to garrison duties in the Middle East before being transferred to North-western Europe on 3 March 1945.