In the First World War, thousands of women played an active part at the front as paramedics and nurses, including the divorced English midwife Elsie Knocker and the wealthy Scotswoman Mairi Chisholm.
The care and medical treatment of wounded soldiers at the front was a chaotic affair. The Belgian Red Cross could not cope with the stream of casualties. Trained and untrained staff were in equally short supply. Help arrived from Great Britain, where dozens of young women volunteered.
Elsie and Mairi had already met before the war through their shared passion for motorcycling. They arrived at the front under the leadership of Dr. Hector Munro. Rejected by the British and French military command, Munro's Ambulance Corps was eventually deployed by the Belgian Field Hospital. The Corps braved dangerous circumstances to rescue casualties from the battlefield and moving them to hospitals further from the front.
 

Elsie Knocker and Mairi Chisholm in front of their first-aid-post in Pervyse in 1918, Public Domain (The Illustrated War News)
Elsie and Mairi, however, wanted to do more. They wanted to provide first aid closer to the front, feeling that too many casualties did not survive the trip to the hospital. Munro would not allow it but Elsie and Mairi persevered. They left the Corps to open a first-aid post in a ruin in Pervyse, less than one hundred metres from the trenches, with two of their colleagues. No longer connected to the Red Cross, they operated completely independently.
Only Elsie and Mairi saw it through. They were the only women to work so close to the front lines of the Western Front, going against the wishes of the British and French army command. They stayed at their post for three years, leaving it only for fund raising trips in Great Britain, and Elsie for a short honeymoon with a Belgian pilot. Mairi's fiancé, also a pilot, died in a crash. In the spring of 1918, they narrowly escaped a poison gas attack, and the Belgian army shut down the first-aid post shortly afterwards.
On the website of the Imperial War Museum, you can listen to a short interview with Mairi Chisholm.