During the First World War, the regiment served with great gallantry on the Western Front in 1914–15, fighting in the Battles of Givenchy, Neuve Chapelle, Aubers Ridge, the Second Battle of Ypres and the Battle of Loos. Lieutenant William Bruce was awarded the Victoria Cross during the Battle of Givenchy. In 1916, the regiment arrived in Mesopotamia. Here, it fought in the bloody battles for the Relief of Kut al Amara on the Tigris Front in 1916–17, the capture of Baghdad, and in operations north of Baghdad at Daur and Tikrit. For its gallant conduct during the war, it was made a "Royal" battalion in 1921.