Heath served in the First World War with the 110th Mahratta's, seeing action in the Mesopotamian campaign. He spent two and a half years in Mesopotamia, where he was twice wounded and invalidated with heat stroke in August 1915, and prior Siege of Kut he had been appointed governor of Qurna. He was promoted to major in August 1915, and was decoated by the Kingdom of Serbia in 1916 with the Order of Karađorđe's Star, 4th Class (with swords). In June 1917, he was made a temporary lieutenant colonel while commanding a battalion. Heath died in July 1917 at Baghdad from the effects of heat. He was survived by his wife, Pear St John Richardson, who he had married at Poona in 1906, having one son.