'Vercors' was a German operation, otherwise known as 'Bettina', to retake the Vercors massif in south-eastern France from the Maquis du Vercors (21 July/5 August 1944).

Located to the west of the Rhône river, to the south-west of Lyon, this massif is 30 miles (48 km) long and 12 miles (19 km) wide at an altitude of 3,000 ft (915 m), and was used by the 4,000-strong Free French resistance group known as the Maquis du Vercors, led by François Huet, as a refuge and a sanctuary for the resistance forces during the period of the German occupation of France.

Lying between the Rhône river and the Franco/Swiss frontier, the area of high forested mountains and hills, cut by many rivers, was ideal terrain for the French resistance forces which, in March 1944, were amalgamated as the Forces Françaises de l’Intérieur. From north to south, the primary FFI groups of 1944 were the Maquis de l’Ain et du Haut-Jura attacked in 'Korporal' (5/13 February), 'Frühling' (7/18 April) and 'Treffenfeld' (7/19 July), the Maquis de Glières attacked in 'Hoch-Savoyen' (26/30 March), the Maquis des Bauges attacked in 'Bauges' (3/6 July), the apparently unamed maquis grouping between Albertville and Bourg St Maurice attacked in 'Hochsommer II' (10/16 August), the Maquis de Chartreuse, the Maquis de la Belledonne and Maquis de l’Oisans attacked in 'Hochsommer I' (8/18 August), and the Maquis du Vercors attacked in 'Vercors'.

In the period 16/24 April 1944, elements of the collaborationist Milice Franc-Gardes attacked the village of Vassieux en Vercors, burning several farms and either killing or abducting some of the inhabitants, but even then the local population remained loyal to the resistance. On 5 June the Free French government in London called upon the people of the Vercors to attempt to slow the advance of any German formations heading north toward Normandy, and at the same time the French French wished to exploit the area’s relative impenetrability for the creation of a national redoubt in which resistance forces could gather and then make sorties against the lines of communication of General Friedrich Wiese’s 19^th Army after the 'Dragoon' (i) landing of Lieutenant General Alexander McC. Patch’s US 7^th Army in southern France on 15 August 1944.

Believing that they would soon receive reinforcements and heavy weapons flown in by air, the Free French closed the passes to the Vercors on 10 June, a number of towns and villages on the plateau declared themselves free of German occupation, and on 3 July 1944 the area was proclaimed the Free Republic of Vercors, the first democratic place in France since the beginning of the German occupation in June 1940. The Free Republic of Vercors lasted less than one month, however. After a period of steadily more intense skirmishing between the resistance forces on the one hand and the Germans and Milice Franc-Gardes on the other, on 19 July the Germans launched a major land assault, supplemented three days later by the gliderborne landing of 200 SS troops.

Despite the admittedly limited support which could be afforded by weapons drops and the arrival of missions despatched by the Special Operations Executive and Office of Strategic Services, the resistance forces could not check the brutal German-led suppression of the uprising by terrorisation of the plateau’s population and the killing some 639 members of the resistance forces as well as 21 civilians.

For this task, aided by the French collaborationists Jacques de Bernonville and Raoul Dagostini with 500 Milice Franc-Gardes, the Germans deployed between 8,000 and 10,000 men under Generalleutnant Karl Pflaum, commander of the 157^th Reserve-Division, which contributed four battalions of the 1^st Reserve-Gebirgsjägerregiment, two battalions of the 157^th Reserve-Grenadierregiment and two artillery batteries of the 7^th Reserve-Artillerieregiment. Other units included the Kampfgruppe 'Zabel' (one infantry battalion of Generalleutnant Erwin Jollasse’s 9^th Panzerdivision and one Ostbataillon of eastern European volunteers), three Ostlegionen battalions, about 400 paratroopers, about 200 military policemen, one battalion of the 200^th Sicherungsregiment, and one battalion of the 19^th SS Polizeiregiment. The German and collaborationist losses were in the order of 150 men.