They were assigned to the Corps Expéditionnaire d’Orient and order to move to Serbia. After boarding the steamship Mossoul in Marseille, they reached Salonika (known as Thessaloniki in modern Greece) on 3 November, where they took the night train north to Ghevgheli (now Gevgelija in modern North Macedonia), on the Serbian side of the Greek border. They set up a hospital in an unused silk factory where they treated 100 patients with injuries ranging from frostbite to severe lung and head wounds. Following defeats at the hands of Bulgarian forces, Edith and her staff retreated to Salonika by 6 December 1916. Eleven days later, they had re-established the hospital on a drained low swamp by the sea, and by New Year's Day 1917 Edith had the lights on and the x-rays working. Despite the lack of equipment and resources, she established an electrotherapy department and various equipments for the muscular rehabilitation of the soldiers in their care. She also assisted with problems on two British hospital ships, on which the x-ray systems had been damaged during a storm, and gave support to the SWH unit in Ostrovo (now Arnissa on Lake Vegoritida formerly lake Ostrovo in Northern Greece), which arrived during September 1916. She had a break for sick leave in December 1917 and returned until the following summer. She applied for an appointment as an army camp radiologist in Salonika, but her demand was blocked by the War Office. In October 1917, she returned to France to lead the x-ray departments at the SWH hospitals of Royaumont and Villers-Cotterêts. In March 1918, she had to supervise a camp closure and retreat for the third time, when Villers-Cotterêts was overrun by the German troops. During the final months of the war the fighting intensified and there was a steep increase in workload; in the month of June alone the x-ray workload peaked at over 1,300, partly because of an increased use of fluoroscopy.