The beginning of August 1644 saw the two greatest French men of the war of the mid-17th Century, Turenne and the future Grande Conde, who tried to dislodge the Bavarian general Franz von Mercy from the heights of Frieburg in the black forest. The battles of August 3rd and the 5th were among the most difficult that the two men had conducted throughout their careers. Their carefully prepared plans, we thwarted by the sagacity of the Bavarians where the unfortunate initiative of a subordinate should have been given more time to work. The fights were deadly and they drew a few tears from Mazarin. The days of Fribourg are the fascinating framework of action where obstinacy replaces courage. Thanks to the numerous contemporary testimonies, the reader is immersed in the heart of two battles that helped the French to hunt the Bavarians on the right back of the Rhine. The study of context of the campaign, the nature of the different protagonists and forces enable the reader to understand the ins and outs.