Turenne had also been in Paris, and had strongly represented to Mazarin the necessity for the armies of France and Sweden in Germany acting together, since while they were acting separately, and at great distances apart, the Austrians and Bavarians could unite and crush the one, while the other could offer it no assistance.  It was owing to this that the conquests made by the troop of France and Weimar had been repeatedly wrested from them.  The cardinal listened to his advice, and determined to bring about a union between the two armies of the confederation.  In the meantime a conference was going on at Munster between the representatives of the various conflicting powers, but each put forward such exorbitant demands that no progress was made.

The Duke of Bavaria, indignant at the small support that Austria had given him, was playing off France against the latter power.  Mazarin was persuaded that he was only waiting for an opportunity to desert the Imperialist cause, and therefore ordered Turenne not to cross the Rhine, as the duke had promised that he would remain neutral unless the French advanced into Germany, when the feelings of his subjects might force him to take the field again on the side of Austria.

Turenne was therefore ordered to besiege Luxembourg.  The marshal, however, had no belief in the Bavarian promises, and on arriving on the Rhine early in April, and seeing that were he to march with his army away to Luxembourg the cause of France and Germany would be lost, he continued to make various excuses for not moving, until the Duke of Bavaria, having obtained many concessions from Austria, threw off the mask, and marching with his army joined that of the emperor in Franconia.  Thus the whole Imperial forces were posted between the French and the Swedes.

Turenne saw that his only hope of success would be to effect a juncture with the Swedes, and wrote to the cardinal to that effect; then, without waiting for an answer, he set his army in motion.  A tremendous circuit had to be made.  He forded the Moselle six leagues above Coblenz, the bridges over the Rhine being all in possession of the enemy, marched up into Holland, and obtained permission from the king to cross at Wesel, which he reached after fourteen days’ march.  Crossing the Rhine on the 15th of July he marched through the country of La Mark, and through Westphalia, and on the 10th of August joined the Swedes under General Wrangel, who had received news of his coming, and had intrenched himself so strongly that the enemy, who had arrived before him, did not venture to attack him.  The enemy now fell back at once and encamped near Freiburg.  Their army was superior in force to that of the allies, they having fourteen thousand horse and ten thousand foot, while the allies had but ten thousand horse and seven thousand foot.  The allies had, however, sixty pieces of cannon against fifty of the Imperialists.  The allies advanced to Freiburg and offered battle, but the Archduke Leopold, who commanded the Imperialists, declined to come out of the great intrenchments he had thrown up round his camp.