 Complete the following phrase:  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 