During the Second World War, French singer Edith Piaf

was stuck in Paris. To stay alive, she had to perform for the Nazis

who occupied the city.  She did and, at the same time,

passed along information she picked up to the French underground.

Toward the end of the war, she suggested she give a concert for the French prisoners  in Paris.

 The authorities agreed and not only allowed her to sing,

but gave her permission to have a photo taken of her

with a host of French prisoners behind. 

What the Nazi authorities did not know was that after she had the photograph, she gave it to the French underground.

They cut out the individual faces of the prisoners

and used them to make identity cards so the French

prisoners who escaped would have ID cards with current portraits.