Campion later commanded 15th (Reserve) Bn Royal Fusiliers in the UK and then went to France to command 6th (Service) Bn Bedfordshire Regiment and 17th (Garrison) Bn Royal Sussex on the Western Front before returning to the 4th Royal Sussex after its arrival from the Mediterranean in 1918. He led the battalion through the final Allied Hundred Days Offensive. He was awarded the Distinguished Service Order in 1918 and continued to command the battalion in the postwar Territorial Army.