But unlike Napoleon, Louis knew when he had gone far enough. He was not going to stake everything on the chance of success in a war against a combination of European powers, which was certain to grow larger as time went on. He had already a securer foundation on which ultimately to raise the edifice of French domination over the Spanish Netherlands in his secret partition treaty with the Emperor. The terms of the Triple Alliance guaranteed to him the possession of Lille, Tournai, and Charleroi, the three fortresses which would make France impregnable on her north-eastern frontier and open to her the gate of the Netherlands. The show of moderation at this juncture would do much to disarm the suspicion of Europe, would give him time to mature his plans for the future, and enable him to make very substantial additions to his power in the present. So Louis declared himself willing to negotiate for peace, and on May 29th, 1668, the treaty of Aix-la-Chapelle was signed between France and Spain. By it France gave back Franche Comté, having dismantled the fortresses, and received Charleroi, Binch, Ath, Douai, Tournai, Oudenarde, Lille, Armentiéres, Courtrai, Bergues and Furnes, with their districts. Some of these towns, such as Courtrai, Oudenarde and Ath lay within the Netherlands, but in the line of fortresses which stretched, roughly speaking, along the frontier from Dunkirk to Charleroi, and included Lille, France had now an adequate defence for her capital. Paris was safe and the invasions of the years of the _Fronde_ could never again recur.