To make easier Rhône crossing between the two armies, two bridges were kept intact: between Sarras and Saint-Vallier and between Tournon-sur-Rhône and Tain-l'Hermitage.
A SECOND FRONT LINE
The line of defence on Ardèche side was 30 km further north than that on Drôme, which began at the confluence of the Isère and Rhône rivers, at Pont-de-l'Isère. This gap created a second front line for the German troops. On 21 June, they were engaged in the north of Drôme and immobilized on the Isère, while in Ardèche, the Germans were stopped in front of the Annonay-Andance line.
While in the west, the Leibstandarte SS Adolf Hitler Regiment broke through the French lines and captured Saint-Étienne, 4th Panzer Division tried from 21 June to seize the two bridges at Saint-Vallier and Tain-l'Hermitage: it hoped to catch Second French Army from the rear and lock it into a pocket, leaving it with no other option but to surrender.
Having been withdrawn from the Rhône Defence Sector and retreating from north of Lyon, 1 Spahis Brigade (BS) took over the defence of the northern Ardèche and the part of it along the Rhône corridor, from Andance to Châteaubourg (opposite Pont-de-l'Isère). The brigade was supported by two artillery batteries judiciously positioned on the Ardèche mountains, facing the river, in defence of the two bridges and also in interdiction fire on the Route Nationale 7, to block the units of 4th Panzer Division operating in the Drôme.
Caught under fire from these batteries, 33 Schützen Regiment tried in vain to seize these strategic crossings over the Rhône: here too the enemy failed in its attempts to establish bridgeheads on the rear of the two French armies.
1st BS : 1 Spahis Brigade
4th PD : 4th Panzer Division
33rd SR : 33 Schützen Regiment
LSSAH : Leibstandarte SS Adolf Hitler (reinforced, motorized, regiment)
Chazalon, Thierry. Resistances! Les prémices (juin 1940 – juillet 1941), the Resistance began on 23 June 1940 on the banks of the lower Isère valley. Montélimar: autoédition, 2011. 200 p.