Throughout its existence the brigade was composed almost entirely of battalions of the Lancashire Fusiliers, except for a few brief months in the early half of the Second World War.

In early May 1915, the 42nd Division embarked from Alexandria for Cape Helles on the Gallipoli Peninsula, where Allied troops had landed a few days earlier.

[1] The fighting was "a singularly brainless and suicidal type of warfare",[6] and virtually nothing was achieved in any of these attacks, at the cost of heavy casualties.

[1] In February and March 1917, the whole of 42nd Division moved from Egypt to France to reinforce the British Expeditionary Force (BEF) on the Western Front, where it remained for the rest of the war.

On 6 September 125th Brigade carried out an unsuccessful attack on strongly-held German pillboxes around Iberian, Borry, and Beck House Farms.

Then, during the Allied Hundred Days Offensive, it participated in the Battle of Albert (21–23 August) where Lance Corporal Edward Smith of the 1/5th Battalion, Lancashire Fusiliers was awarded the Victoria Cross.

[1] On the Hindenburg Line it was in the Battle of the Canal du Nord, where the Official History records that 125th Brigade's advance at 07.52 on 27 September 'was met by very heavy fire in front from machine guns which the barrage did not seem to have touched, and from Beaucamp on the right ...

125th Brigade led the attack with two battalions in front, but in spite of a defensive smoke barrage they suffered considerably from enemy shelling during assembly.

The defenders of Beaurain "made a stout resistance and there was hard fighting in the early stages of the attack, men on both sides being killed by the bayonet".

[16] The 125th Brigade, commanded at the time by Brigadier George Sutton a Territorial officer, landed in France on 15 April 1940 with the rest of the 42nd Division and became part of the British Expeditionary Force (BEF).

Both the 42nd and 44th Divisions had, before deployment to France, been held back from reinforcing the BEF in order to participate in potential operations in Northern Europe, although this had never came to fruition.

This was part of the BEF's official policy of mixing the Regular and Territorial Armies and was intended to, in theory, strengthen the TA divisions.

[18][19] After the defeat at the hands of the German Army during the Battle of France, the brigade, after sustaining very heavy casualties, was evacuated from Dunkirk on 30 May 1940.

With the 42nd Division, the brigade would spend most of its time in the United Kingdom reforming and absorbing large numbers of men who had been conscripted into military service as replacements, on home defence and training to repel an expected German invasion.

When the 10th Armoured Brigade was scheduled for disbandment in late 1943, Members of Parliament for the Lancashire towns complained about the loss of their Territorial battalions.