After the Normandy Invasion of 6 June 1944, the leadership of a force of about 4,000 maquis declared the Free Republic of Vercors and attempted to create a conventional army to oppose the German occupation.

The porous limestone rocks and karst terrain result in an extensive system of caves, caverns and a scarcity of surface water in the form of streams, springs and shallow wells.

by the early months of 1943, the forest and fastnesses of places like the Vercors had become home and refuge to a polyglot collection of the elements of defeated France: its new generations, its old administrators, its competing political parties, its heterodox communities and the scattered fragments of its once proud army.

To avoid the STO, tens of thousands of men fled into the mountains and forests of France and joined the maquis, the rural resistance fighters against the German occupation.

[13] In 1943, three men, mountaineer Pierre Dalloz, soldier Alain Le Ray, and writer Jean Prévost planned to use the Vercors as a redoubt and a staging area for resistance to the German occupation.

[15] In August 1943, Francis Cammaerts, code-name Roger, an agent of the British Special Operations Executive (SOE) organization, journeyed to the Vercors and met with French soldier Eugène Chavant.

[16] The Germans had no soldiers stationed on the Vercors Massif but in response to sabotage activities of the maquis conducted periodic raids usually launched from Grenoble.

The contradictions are illustrated by the differences in the D-Day messages of the Allied commander, Dwight D. Eisenhower, and the Free French leader, Charles de Gaulle.

On D-Day, Cammaerts on the Vercors Massif gave the message to the maquis that clandestine sabotage should continue, but it should remain hidden, as "it would be at least two months before they would be needed".

To the contrary, on June 8, Marcel Descour, the regional leader of the French Resistance, instructed Francois Huet, the new commander of the Vercors maquis, to mobilise.

The maquis also anticipated incorrectly that Allied paratroopers would land on the massif to assist it and that it would be supplied with anti-tank and other heavy weapons to fight the Germans.

[25] While François Huet was attempting to create a conventional army from the maquis, journalist and De Gaulle supporter Yves Farge was organizing the politics of the Vercors resistance.

[26][27] On 14 July, 72 American B-17 bombers dropped by parachute 870 CLE Canisters containing weapons, including supplies and anti-tank Bazookas, to the Maquis of Vercors.

The maquis commander Huet had a meeting of his leaders and they decided to continue to fight until defeat was inevitable and then disperse to the forest and mountains of the massif, anticipating that the Germans would soon withdraw.

It was also decided that Huet's superior officer in the FFI, Henri Zeller who was present at the meeting, would escape the Vercors with SOE agents Cammaerts, Granville, and wireless operator Auguste Floiras to coordinate the resistance in other areas.

[38] On 21 July 1944, about 200 men from Fallschirm-Bewährungstruppe (probationary troops) forming the Fallschirm-Kampfgruppe "Schäfer",[37] with several French volunteers (from the Sipo-SD of Lyons or from the 8th Company of the 3rd Regiment "Brandenburg"), were airborne in 22 DFS-230 gliders (each with 1 pilot and 9 soldiers) towed by Dornier-17 bombers of I/Luftlandegeschwader 1, from Lyons-Bron to Vassieux-en-Vercors.

[40][page needed] Lieb specifies that the commander of the Sipo-SD of Lyon (KDS), SS-Obersturmbannführer (SS Lieutenant Colonel) Werner Knab, was also airborne on Vassieux on 21 July.

It was made up of volunteers out of Fallschirmjäger-Bewährungstruppe (probationary troops), mustered at Tangerhütte and trained for three months at Dedelstorf in order to launch an attack from gliders.