Gwynne-Vaughan was appointed Chief Controller of the WAAC Overseas, leading operations in France and Belgium.
In March 1917, Helen Gwynne-Vaughan was appointed Chief Controller of the Women's Army Auxiliary Corps (WAAC) Overseas, a role that placed her in direct charge of organizing and running the Corps' operations in France and Belgium during the height of the First World War.
This appointment was historically significant because it represented one of the first instances of a woman holding substantial command authority over British military personnel operating in an active theatre of war. The WAAC had been formed in response to the urgent need to free up men for frontline combat by employing women in administrative, technical, and logistical support roles, including cooking, clerical work, and vehicle maintenance.
Gwynne-Vaughan's scientific background as a trained botanist gave her a rigorous, methodical approach to organization and discipline that she applied to building an effective corps structure overseas, often under difficult and dangerous wartime conditions, including the threat of German bombing raids near the front lines. Her leadership helped establish standards of conduct, welfare, and organizational discipline for women in military auxiliary roles that would influence subsequent women's services.
Her success in this overseas command directly informed her later, even more senior appointments, cementing her reputation as one of the foremost female military administrators of her generation.