Prince Leopold having accepted the crown, the new treaty was sanctioned by the Belgian Congress on July 9th. Less than a month later, on August 2nd, the Dutch armies, breaking the armistice, invaded Belgian territory and defeated the Belgian forces at Louvain. Owing to the armed intervention both of England and France, the Dutch were forced to retreat, but these military operations had set the seal on Belgian hopes.
The Powers were now "firmly determined to stop, by all available means, the resumption of hostilities which would threaten Europe with a general war," and, on November 15th, King Leopold was obliged to accept, under strong protest, a new agreement, known as "the Treaty of XXIV Articles," which, though preserving the country's independence and neutrality, deprived her of her natural frontiers and tore from her territories whose inhabitants had shared her life since the early Middle Ages. The Scheldt was given the status of an international river, according to the General Act of Vienna, the supervision of pilotage, buoying and dredging operations being entrusted to a Dutch-Belgian commission. Belgium retained half of Luxemburg (the area known to-day as the province of Luxemburg), while the other half, with the town of Luxemburg, remained in the hands of the Dutch king, and constituted a Grand Duchy attached to the German Confederation. "In exchange" for their portion of Luxemburg, the Belgians were obliged to relinquish their rights over Eastern Limburg and Maestricht, which became the Dutch provinces of the same name. Such were the "final and irrevocable" decisions of the Powers.
Though the compromise was entirely in his favour, King William refused to sanction it. From the beginning of the negotiations the Dutch had contended that, by the separation of Belgium and Holland, Article XIV of the treaty of Münster (that is to say, the right of Holland to close the Scheldt in time of peace or war) came into force again. Disregarding the liberal principles laid down at Vienna, they wanted to go back to the old régime of the seventeenth and eighteenth centuries which subjected Belgium to their control. Holding Maestricht, the key of the Meuse, and the Lower Scheldt, the key of Antwerp, they intended to treat independent Belgium as they had treated the Spanish and Austrian provinces.