Excluded from the planning for the Normandy Landings, and his staff devised an operation called "Plan Caïman" in which French paratroopers would join the maquisards of the Massif Central to liberate the surrounding area and from there establish contact with the invading British and US forces. The Allied planners rejected the plan on the grounds that they would not have the resources to support it. On 20 May 1944, the Maquis du Mont Mouchet in the Massif Central staged an open uprising on its own initiative and was crushed within three weeks with the usual reprisals. Despite this, on 6 June, broadcast an impassioned call to arms to the French people on the BBC, which the maquisards interpreted as a signal for overt action; a lower-key message from Eisenhower to avoid a "premature uprising" was widely ignored. As a direct consequence, in July the 4,000 FFI on the Vercors Plateau near Grenoble were attacked by a German force of 10,000 including paratroopers and troops in gliders. In the Battle of Vercors, the lightly armed French defences were overwhelmed, despite assistance from Allied agents, air-drops and special forces.