On the outbreak of the First World War in August 1914, the 1st Cameronians were one of four independent battalions earmarked for service with the British Expeditionary Force as line of communications troops. They landed in France on 11 August, and on 22 August all four were grouped into the 19th Infantry Brigade for frontline service. Under Robertson's command, the battalion first saw action on 23 August at the Battle of Mons, where the 19th Brigade held the far left of the British line, It served in reserve during the Battle of Le Cateau, covering the retreat of the 5th Division at the end of the day's fighting.