The pourparlers at Nijmwegen were still going on, but made no progress in face of William's refusal to treat except in concert with his allies. Louis XIV, however, fully informed of the state of public opinion and of the internal dissensions both in the United Provinces and in England, was not slow to take advantage of the situation. A powerful French army invaded Flanders and made themselves masters of Ypres and Ghent and proceeded to besiege Mons. William, despite the arrival of an English auxiliary force under Monmouth, could do little to check the enemy's superior forces. Meanwhile French diplomacy was busy at Amsterdam and elsewhere in the States, working against the war parties; and by the offer of favourable terms the States-General were induced to ask for a truce of six weeks. It was granted, and the Dutch and Spanish representatives at Nijmwegen (those of the emperor, of Brandenburg and of Denmark refusing to accede) speedily agreed to conclude peace on the following terms: the French to restore Maestricht and to evacuate all occupied Dutch territory, and to make a commercial treaty. Spain to surrender an important slice of southern Flanders, but to be left in possession of a belt of fortresses to cover their Netherland possessions against further French attack. But, though these conditions were accepted, the French raised various pretexts to delay the signature of the treaty, hoping that meanwhile Mons, which was closely beleaguered by Luxemburg, might fall into their hands, and thus become an asset which they could exchange for some other possession. The States and the Spanish Government were both anxious to avoid this; and the Prince of Orange, who steadily opposed the treaty, returned towards the end of July to his camp to watch the siege of Mons and prevent its falling into the hands of the enemy. At the same time (July 26) King Charles, who had been working through Sir William Temple for the conclusion of peace, now declared that, unless the treaty was signed before August 11, he would assist the allies to enforce it. The French diplomatists at Nijmwegen had hitherto declared that their troops would not evacuate Maestricht and the other places which they had agreed to restore to the States, until Brandenburg and Denmark had evacuated the territory they had conquered from Sweden. On August 10, just before time for resuming hostilities had been reached, they tactfully conceded this point and promised immediate evacuation, if the treaty were at once concluded. Van Beverningh and his colleagues accordingly, acting on their instructions, affixed their signatures just before midnight.
They fell into the trap laid for them, for the treaty between France and Spain was not yet signed, and it was the intention of the French to make further pretexts for delay in the hope that Mons meanwhile would fall. The report of the conclusion of peace reached the stadholder in his camp on August 13, but unofficially. On the morning of August 14 D'Estrades came personally to bring the news to Luxemburg; and the French marshal was on the point of forwarding the message to the Dutch camp, when he heard that Orange was advancing with his army to attack him, and he felt that honour compelled him to accept the challenge. A sanguinary fight took place at St Denis, a short distance from Mons. William exposed his life freely, and though the result was nominally a drawn battle, he achieved his purpose. Luxemburg raised the siege of Mons, and the negotiations with Spain were pressed forward. The treaty was signed on September 17, 1678. The peace of Nijmwegen thus brought hostilities to an end, leaving the United Provinces in possession of all their territory. It lasted ten years, but it was only an armed truce. Louis XIV desired a breathing space in which to prepare for fresh aggressions; and his tireless opponent, the Prince of Orange, henceforth made it the one object of his life to form a Grand Alliance to curb French ambition and uphold in Europe what was henceforth known as "the Balance of Power."
In setting about this task William was confronted with almost insuperable difficulties. The Dutch people generally had suffered terribly in the late invasions and were heartily sick of war. The interest of the Hollanders and especially of the Amsterdammers was absorbed in the peaceful pursuits of commerce. The far-reaching plans and international combinations, upon which William concentrated his whole mind and energies, had no attraction for them, even had they understood their purpose and motive. The consequence was that the prince encountered strong opposition, and this not merely in Holland and Amsterdam, but from his cousin Henry Casimir and the two provinces of which he was stadholder. In Amsterdam the old "States" party revived under the leadership of Valckenier and Hooft; and in his latter days Van Beuningen was ready to resist to the utmost any considerable outlay on the army or navy or any entangling alliances. They held that it was the business of the Republic to attend to its own affairs and to leave Louis to pursue his aggressive policy at the expense of other countries, so long as he left them alone. The ideal which William III had set before him was the exact reverse of this; and, unfortunately for his own country, throughout his life he often subordinated its particular interests to the wider European interests which occupied his attention.