The War of Devolution lasted from 1667 to 1668. The well-disciplined and splendidly generaled armies of Louis XIV had no difficulty in occupying the border fortresses in the Spanish Netherlands. The whole territory would undoubtedly have fallen to France, had not a change unexpectedly occurred in international affairs. The trade war between England and Holland came to a speedy end, and the two former rivals now joined with Sweden in forming the Triple Alliance to arrest the war and to put a stop to the French advance. The "balance of power" demanded, said the allies, that the other European states should combine in order to prevent any one state from becoming too powerful. This plea for the "balance of power" was the reply to the French king's plea for "natural boundaries." [Sidenote: Treaty of Aix-la-Chapelle, 1668] The threats of the Triple Alliance caused Louis XIV to negotiate the treaty of Aix-la-Chapelle, by which Spain surrendered to France an important section of territory in Flanders, including the fortified cities of Charleroi, Tournai, and Lille, but still retained the greater part of the Belgian Netherlands. The taste of the Grand Monarch was thereby whetted, but his appetite hardly appeased. [Sidenote: Franco-Dutch Rivalry] Louis blamed the Dutch for his rebuff. He was thoroughly alive to the fact that Holland would never take kindly to having powerful France as a near neighbor, and that French acquisition of the Belgian Netherlands, therefore, would always be opposed by the Dutch. Nor were wounded vanity and political considerations the only motives for the Grand Monarch's second war, that against the Dutch. France, as well as England, was now becoming a commercial and colonial rival of Holland, and it seemed both to Louis XIV and to Colbert that the French middle class would be greatly benefited by breaking the trade monopolies of the Dutch. Louis's second war was quite as much a trade war as a political conflict. [Sidenote: Civil Strife in Holland]