http://thefederalist.com/2018/06/09/meet-virginia-hall-one-of-the-unsung-heroes-of-d-day/
In the spring of 1944, behind enemy lines in occupied France, members of the French Resistance stayed close to their wireless devices, awaiting their call to action. Broadcasting from London, announcers at Radio Londres sent coded instructions to various Resistance factions, disguised as “Personal Messages.” The messages were specifically designed to sound silly but familiar, and as they weren’t a cipher, they drove the Axis powers mad trying to break their code.
Allied forces inundated the broadcasters with codes to send out, knowing that the invasion was in the planning stages, but coming soon. The Allies were depending on the Resistance to choke the German supply lines on the French railroad, and clear the way for their entry into France.
On June 5, as the allies prepared to launch Operation Overlord, a poem familiar to every French man and woman crackled over the airwaves, “Chanson d’automne.” The Resistance had been waiting for months to hear the prose of Paul Verlaine’s 1860 poem.
“Les sanglots longs
Des violons
De l’automne”
The first three lines served as a warning that the invasion would begin within 2 weeks
“Blessent mon cœur
D’une languer
Monotone”
The final part of the message indicated that the invasion would reach France in 48 hours. It was time. This was their official call to action. Plans to sabotage the German supply lines were to be enacted at once.
Outside of the Resistance, there were already members of the Allied Forces behind enemy lines, assisting the Resistance and paving the way for victory in France. Among them, Virginia Hall, a young American woman. Hall had already spent years living in occupied France, gathering information for the British Special Operations Executive (SOE). Early in her assignment, she lived openly as an American, though with a code name, masquerading as a journalist, while actually wreaking havoc on the Germans as an Allied spy. When The United States entered the war in 1942, and Germany officially seized the remainder of France, Hall was forced to flee the country — but she wouldn’t stay away for long.