In 1909 it was decided to form Voluntary Aid Detachments (VADs) to provide medical assistance in time of war. By the summer of 1914 there were over 2,500 Voluntary Aid Detachments in Britain. Of the 74,000 VADs in 1914, two-thirds were women and girls.  

Katharine Furse took two VADs to France soon after the outbreak of the First World War. After establishing a hospital at Boulogne, Furse returned to London where she became Commander-in-Chief of the organisation. During the next four years 38,000 VADs worked as assistant nurses, ambulance drivers and cooks. VAD hospitals were also opened in most large towns in Britain.  

At first the military authorities were unwilling to accept VADs on the front-line. However, this restriction was removed in 1915 and women volunteers over the age of twenty-three and with more than three months experience, were allowed to go to the Western Front, Mesopotamia and Gallipoli. Later VADs were sent to the Eastern Front.

Some women went to the Western Front as letter writers for soldiers who were either too ill or too illiterate to write their own letters. May Bradford, the wife of John Rose Bradford, Physician to the British Expeditionary Force, later recalled how she educated men on the treatment of women: "To one man I said, 'Shall I begin the letter with my dear wife?' He quietly answered: 'That sounds fine, but she'll be wondering I never said that before.'