While battlefield nurses existed long before the Great War, they were usually attached to a religious organization.  Most nurses were nuns, for whom nursing was a holy duty, one done in service to God by emulating the healing works of saints and prophets.  Following the work of women such as Mary Seacole and Florence Nightingale in the latter half of the 19th century, nursing became a secular and specialized profession in Britain.  By the 1910s, there were numerous nursing schools and training hospitals across Europe, especially in Britain, and every army had official nursing units and divisions attached to their medical corps.  Britain had the VAD (Voluntary Aid Detachment) and FANY (First Aid Nursing Yeomanry).  The VAD were not explicitly military women, like the FANY were, but VADs were mobilized by the British military during the war to supplement and assist on the front.  Germany had an estimated 92,000 nurses scattered among hospital and medical detachments in their own military, usually as members of an existing unit.  The United States, meanwhile, had an official Army Nurse Corps founded in 1901, with a sister Navy Nurse Corps following in 1908.  In addition to these military units, both sides made use of assistance offered by neutral organizations such as the Red Cross and their own volunteer nurses.

Before the outset of the Great War, the battlefront was seen as a sphere exclusive to men, similar to how reproduction and the home were seen as being exclusive to women.  However, in March of 1917, three years into the war, high casualties on the front led Britain's War Office to create the Women's Army Auxiliary Corps.  It was officially instituted in June, when the first volunteers entered basic training.  As its name implies, the WAAC employed women in auxiliary roles in the British Army, rather than combat roles.  Women would work as cooks, clerks, and mechanics, as well as domestic staff or assistants to officers, but they would not hold rifles or fight in the trenches.  The idea behind this organization was to free up more men to fight on the Western Front, and perhaps save money by paying women far less to do the same jobs as the men they were replacing.  It was apparently very successful, as the Royal Air Force and Navy both implemented their own women's auxiliaries the next year.

Despite the success of the program, not everyone was on board.  The young, mostly single women that joined the WAAC were viewed as glorified tourists, looking for a safe avenue for an adventure.  Even worse, they were believed to have frequently been engaging in sexual trysts with servicemen.  These rumors spurred the government to set up an official enquiry, which interviewed women, checked medical records, and investigated reports from the women's supervisory officers.  In all, they found that members of the WAAC not only did their jobs well, but that unmarried servicewomen had a lower pregnancy rate than that of unmarried civilians back home.  It should also be noted that even though servicewomen did not sit in the trenches, they were still at risk.  A full casualty list is hard to come by, as the British National Archive lost all but 7,000 records pages of the over 57,000 WAAC servicewomen during a German bombing campaign.  However, five military honors medals were given to servicewomen for bravery under fire during air raids and shellings, and eight casualties were buried with full military honors after being killed in a bombing raid on a British camp in Etaples, France.  After this incident, the queen lent her name to the organization, renaming the Queen Mary Army Auxiliary Corps as a bit of royal recognition for auxiliaries.

Members of the WAAC, later QMAAC, received less wages, less respect, and more scrutiny from the British public than any male service branch.  They were also not allowed to rise to the rank of a full officer, instead being given the lesser ranks of controllers or administrators.  And, after it and its sister organizations were disbanded in 1921, there were once again little to no opportunities for women to serve in Britain.