Coordination with the French Resistance

French Resistance members and Allied paratroopers discuss the situation during the Battle of Normandyin 1944

Through the London-based État-major des Forces Françaises de l'Intérieur (French Forces of the Interior), the British Special Operations Executive orchestrated a massive campaign of sabotage to be implemented by the French Resistance. The Allies developed four plans for the Resistance to execute on D-Day and the following days:

• Plan Vert was a 15-day operation to sabotage the rail system.
• Plan Bleu dealt with destroying electrical facilities.
• Plan Tortue was a delaying operation aimed at the enemy forces that would potentially reinforce Axis forces at Normandy.
• Plan Violet dealt with cutting underground telephone and teleprinter cables.

The resistance was alerted to carry out these tasks by messages personnels transmitted by the BBC's French service from London. Several hundred of these messages, which might be snatches of poetry, quotations from literature, or random sentences, were regularly transmitted, masking the few that were actually significant. In the weeks preceding the landings, lists of messages and their meanings were distributed to resistance groups. (Wikipedia)