The 7th (Extra Reserve) Battalion was one of only a few SR battalions that was employed for combat during World War I, probably because the Royal Fusiliers had three SR battalions supporting four regular battalions instead of the usual 1:2 ratio. 7th Royal Fusiliers served (alongside the HAC) in 63rd (Royal Naval) Division on the Western Front, seeing a considerable amount of action from the Battle of the Ancre in late 1916. It fought at Arras and Passchendaele, against the German spring offensive and in the Allied Hundred Days Offensive. It was disembodied for the last time on 3 June 1919.