On the outbreak of the First World War, members of the WSPU supported the decision by Emmeline Pankhurst, to help Britain's war effort. In 1914 Eveline Haverfield founded the Women's Emergency Corps, an organisation which helped organize women to become doctors, nurses and motorcycle messengers. Christabel Marshall described Haverfield as looking "every inch a soldier in her khaki uniform, in spite of the short skirt which she had to wear over her well-cut riding-breeches in public."

Appointed as Commandant in Chief of the Women's Reserve Ambulance Corps, in August, 1916, Eveline Haverfield went with Dr. Else Inglis and the Scottish Women's Hospital Units to Serbia. Haverfield's partner, Vera Holme, was commissioned as a major and was placed in charge of horses and trucks in the unit. Other women who served in the unit included Ishobel Ross and Cicely Hamilton.