Each of the 69 line infantry regiments raised one battalion for the First (K1) and for the Second New Armies (K2) designated as Service battalions and numbered after the existing Territorial Force battalions (so 8th and 9th (Service) Battalions for the Northumberland Fusiliers).
While the first four New Armies were being raised, a number of units were also being raised by committees in cities and towns, and by other organizations and individualsthe Pals battalions.