By August 2015, she is believed to have helped around 200 men flee - but her actions violated German military law and she was arrested and charged with harbouring Allied soldiers.
She confessed during her court-martial and despite international pressure, backlash and mass appeals for mercy, she was sentenced to death and shot by a German firing squad in October of that year.
What was the reaction to Edith Cavell's execution?
She helped save the lives of hundreds of people
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Her death was met with widespread condemnation and for years afterwards was used as anti-German propaganda by the British.
In Britain, she became a figure for military recruitment while her death was also used to help boost pro-Allied sentiment in America.
The German government at the time justified the execution, saying they had acted fairly as she had committed treason against Germany by helping the enemy.
But in January the following year, the Kaiser ruled that capital punishment could not be carried out on women without his endorsement.
Edith Cavell quotes
"I can’t stop while there are lives to be saved."
"Patriotism is not enough. I must have no hatred or bitterness for anyone."
"I have no fear nor shrinking; I have seen death so often that it is not strange or fearful to me."
"Someday, somehow, I am going to do something useful, something for people. They are, most of them, so helpless, so hurt and so unhappy."