Marcus forged his father's consent to join the Manchester Regiment aged 14 or 15 as a band-boy. The regiment was sent to Egypt in 1882, and talked his way into being attached to a battery of the Royal Horse Artillery as a bugler so he could take part in a campaign, for which he then received the Khadiva and Egypt medals for.

Marcus reenlisted at the outbreak of the Boer War in 1899 and served in South Africa for some time, before being sent back to England and posted to the Regimental HQ where he reached the rank of Quartermaster Sergeant.

Marcus was called up to the Manchesters on 4th August 1914 to serve as a Corporal.

To his chagrin he was not sent to France, but to an internment camp in Wales guarding 'enemy aliens', many of which he knew as members of the Manchester Jewish Community.

Later Marcus was posted to a Prisoner of War camp, where his knowledge of German got him the job of interrogating prisoners.

In 1916 he was given honourable discharge and received the Silver War Badge for his service.