When the First World War broke out, Anderson and Flora Murray founded the Women's Hospital Corps (WHC), and recruited women to staff it.[9] Believing that the British War Office would reject their offer of help, and knowing that the French were in need of medical assistance, they offered their assistance to the French Red Cross.[10] The French accepted their offer and provided them the space of a newly built hotel in Paris as their hospital.[11] Murray was appointed Médecin-en-Chef (chief physician) and Anderson became the chief surgeon.[10]