Deakin was in London when the First World War broke out, but soon returned home where she joined the
Australian Red Cross and completed a course in nursing. In early 1915, she accompanied her parents to the
Pan Pacific Exhibition in
San Francisco, where her father was the Australian representative. On 21 October 1915, aged 23, Deakin opened the Australian Wounded and Missing Enquiry Bureau in Cairo, with herself as secretary and Johnson as assistant secretary. In May 1916, the bureau moved its headquarters to
Victoria Street, London, after the AIF was transferred to the
Western Front. By late 1917, Deakin was managing 60 staff – including agents in Britain, France, and Belgium – and the bureau had to relocate to a larger building in
Grosvenor Place. Deakin later recalled "we were often met with suspicion and eventually jealousy, as we had made ourselves felt as a court of appeal for relatives who were unsuccessful in obtaining satisfaction from the military authorities". She was succeeded as head of the bureau by
Lilian Avis Scantlebury in 1919. Scantlebury had been with the bureau since 1916 and had led the letter section. ==Marriage and children==