Mairi Chisholm and Elsie Knocker were two British nurses and ambulance drivers whose staggeringly heroic efforts during World War I saved countless lives and earned them life-long honor. They were especially known for their determination to treat wounded soldiers on the front lines instead of transporting them at great risk to "safer" hospital facilities, even though many of their actions went directly contrary to official bureaucratic regulations. In November of 1914, they took the step for which they are most famous. They decided to leave the corps and set up their own dressing station five miles east in a town named Pervyse, north of Ypres, just one hundred yards from the trenches. Her...