At the outbreak of the war, the regiment was an unbrigaded unit of the 5th (Mhow) Division of the Indian Army. However, in 1914 it joined the Army's 3rd (Lahore) Division as part of its 9th (Sirhind) Brigade, landing at Marseilles on 26 September 1914 and taking part in Winter Operations (1914–1915), the Battle of Neuve Chapelle (10–13 March 1915), the Battle of Aubers, the Battle of Festubert (15–25 May 1915), and the Battle of Loos subsidiary attack at the Moulin-du-Piètre on 25 September 1915. The 125th left the 3rd Division in 1915 to join the 7th (Meerut) Division. As part of the 7th Division's 21st (Bareilly) Brigade, the regiment sailed from Marseilles to go to Mesopotamia, landing at Basra on 31 December 1915 and taking part in the attempt to relieve the besieged garrison of Kut al Amara. It proceeded under Allenby to Palestine, and arrived at Suez on 13 January 1918.