A French army of 16,000, led jointly by Condé and Turenne, sought to relieve the town, which had recently surrendered to a Bavarian force under Franz von Mercy.

Having captured Freiburg on 28 July, Mercy placed his men in strong defensive positions on the hills outside the town, which the French attacked on 3 and 5 August.

On 9 August, Mercy learned a detachment under Turenne was marching into his rear to cut off his supply lines, and ordered a general retreat, leaving a garrison in Freiburg.

Mercy was ordered to suspend offensive operations, ceding France the strategic initiative, and allowing Condé and Turenne to take control of most of the northern Upper Rhine.

It was ultimately agreed Condé would assault Mercy's defences on the Schönberg which blocked the main road into Freiburg, while Turenne made a flanking march via Wittnau against the village of Merzhausen in their rear (see Battle map right).

Although Turenne had finally resumed his advance, many of his men were still coming up, slowed by heavy rain, and at midnight the two commanders agreed to halt operations.

When night came, Mercy had held his ground, but two days of fighting had reduced his force by a third, with the French having lost half the number of men engaged.

While Condé remained in Merzhausen to occupy Mercy, early on 9 August Turenne took 6,000 men and began marching into his rear at Denzlingen, five kilometres north of Freiburg.

The problem was especially acute for his cavalry, essential for covering the retreat but whose combat effectiveness was quickly declining due to lack of forage for their horses.

Leaving a hand-picked garrison to hold Freiburg, on 9 August the rest of his army began falling back on St. Peter, which controlled the road to Villingen.

[4][2] Mercy still controlled most of Swabia, but his losses led Maximilian to ban any further offensive action, while his retreat to Rottenburg left the Upper Rhine exposed.

Turenne convinced Condé not to waste the rest of the summer retaking Freiburg, but instead march north to capture Philippsburg, which surrendered on 12 September.