On the 17th of September the Allies advanced upon the French and offered battle. Saxe answered by retiring to an impregnable position between Tongres and the Demer. There was no occasion for him to fight, when his enemies were short of provisions and their cavalry was going to ruin from want of forage. So there the two armies remained once more, within sight of each other but unwilling to fight, since an attack on the entrenchments of either host would have entailed the certain destruction of the attacking force. But meanwhile the trenches had been opened before Namur by a French corps under the Prince of Clermont, and within nine days the town had fallen. Ligonier again urged his design, for which he had prepared the necessary magazines, to upset Saxe's plans by a dash upon Antwerp, but he could find no support in the council of war; so there was nothing for the Allies to do but to wait until some further French success should compel them to move. Such a success was not long in coming. The castle of Namur surrendered after a miserable defence of but eleven days; Clermont's corps was released for operations in the field, and the Allies were forced to fall back for the protection of Liége. Accordingly, on the 7th of October they crossed the Jaar, not without annoyance from the enemy, and took up a new position, which gave them indeed possession of Liége, but placed them between the Meuse in their rear, and an enemy of nearly twice their strength on the Jaar before their front.[227] [Sidenote: Sept. 29/Oct. 10.]