The Prussian invasion of Holland was a military campaign under the leadership of Charles William Ferdinand, Duke of Brunswick, against the rise of the democratic Patriot movement in the Dutch Republic in September–October 1787 with the aim of disempowering the patriots and disarming the Free Corps, as well as reinstating William V of Orange as hereditary stadtholder in the Dutch Republic.
Background
On 7 June Von Salm-Grumbach was appointed by the Defence Committee in Woerden as commander-in-chief and Quint Ondaatje as liaison officer of the troops in Holland. Salm was not recognized by all officers, and his new powers were legally controversial. On the 28 June, he marched to Woerden to capture princess Wilhelmina of Prussia, the wife of the Prince of Orange. At the end of July Salm ordered conquering Palace Soestdijk and besieging Amersfoort.
First came the arrest at Bonrepas of Stadtholder's wife, Wilhelmina of Prussia, on her way from Nijmegen, where William V had taken refuge, to The Hague. There she intended to request her husband to be allowed to return to, after the States of Holland had fired him as Captain General of their troops in 1786. This had not been done on a whim: the decision to travel to The Hague had only been taken after Gijsbert Karel van Hogendorp had undertaken a secret mission to the Orangist leaders in that city to discuss its advisability, because her husband was, as usual, hesitating about what course of action to follow. The leader of the Orangist party in The Hague, the British envoy James Harris saw possibilities to put pressure on the States of Holland if the Princess suddenly arrived, and he told van Hogendorp to give the green light to the Princess, who was with her husband in the armed camp of the Dutch States Army in Amersfoort. The stadtholder then grudgingly gave his consent.
The Princess then returned to Nijmegen, while preparations for the journey to The Hague were made by ordering fresh horses for her carriages along the route in two places. This caused suspicion among the Patriot Free Corps in the area, who in this way were alerted to her supposedly secret travel plans. The military authorities posted Free Corps patrols in the affected area with orders to intercept her. When on 28 June 1787 she departed from Nijmegen to The Hague with a small retinue (a chamberlain, a lady in waiting, and two officers, colonel Rudolph Bentinck, an adjutant of the stadtholder, and Frederick Stamford, the military tutor of her sons), but no armed escort (Harris had advised it was safe enough to only take a bag of gold along to bribe Patriot Free Corps with) she was indeed intercepted near Goejanverwellesluis by a Free Corps patrol from Gouda. She was not mistreated, as has been asserted by Orangist propagandists, but only temporarily detained in a nearby farm, to await the arrival of members of the Military Commission in Woerden. The only untoward thing that happened was that the leader of the patrol drew his saber, but he put it back in its scabbard when requested. When the Military Commission arrived she was told she would not be allowed to proceed to The Hague, for fear of instigating public unrest there, but she was immediately released, and allowed to return to Nijmegen.
Diplomatic preliminaries
Meanwhile, Harris in The Hague was worried about the lack of news about the Princess. He was playing cards with the French envoy Vérac that evening, and was so off his game that he lost a lot of money. As soon as he received news about the interception, he regained his composure, and started to take advantage of the situation, thereby supporting the suspicion on the part of the French and the Patriots that he had all the time conspired to bring the event about, and that it was no more than a provocation. And this was more or less the consensus in diplomatic circles in The Hague, though hypotheses about who actually conspired with whom varied.
In any case, the Princess, back in Nijmegen, on 29 June wrote letters of complaint to her husband's nephew, king George III of Great Britain, and her brother king Frederick William II of Prussia. Her husband was little help: he wrote to his daughter, Princess Louise: "The misfortune which I foresaw has happened ... I was always against this journey and in my misfortune it is a great consolation that I did what was in my power to stop it and to dissuade your Mother from such a risky venture."
Though the Princess did not expect much from her brother at first, her message fell onto fertile ground. Since the death of his predecessor Frederick the Great the previous year, the new king had given new hope to the pro-British court party around minister Hertzberg, and lessened the influence of the pro-French party of Hertzberg's rival, minister Finckenstein. Hertzberg was opposed to the alliance between France and Austria which at the time held the upper hand on the European Continent, and the détente the old Prussian king had maintained with France, and which had previously held Prussia back from all too aggressive interventions in the Dutch Republic that might offend France. The incident with the Princess played into his hands. Fredrick William's first impulse was rage; he instructed the Prussian envoy in The Hague, Thulemeyer to protest to the States General of the Netherlands about the insult to his sister, and to demand from the States of Holland that they would give her satisfaction, though this protest did not yet take the form of an ultimatum.
The Princess saw the possibilities immediately: she wrote a letter to her brother on 13 July in which she proposed that he would use the situation to bring about the restoration of her husband to his office of Captain-General and to liberate the Republic from the Patriots. But she overplayed her hand, because at this time Frederick was only interested in an apology, and did not conflate this with something that might frustrate the attempts at mediation France and Prussia had previously made. Stamford, who had conveyed the Princess's letter by hand, heard the king exclaim: "The b... wants to draw me into a war, but I'll show her that she doesn't lead me." Envoy Thulemeyer also played a moderating role, be it with questionable means, as he lied both to the Dutch politicians and his own government about what either had actually said, so as to calm tempers on both sides. When the Princess became aware of this double play, she started to work for Thulemeyer's recall. Thulemeyer also tried to cool the Prussian ardor by exaggerating the rumors about French preparations for war in case of a Prussian intervention in the form of establishing an armed camp in Givet on the border between France and the neutral Prince-Bishopric of Liège, that provided a theoretical route for a French army to the Netherlands, that circumvented the Austrian Netherlands.
The camp in Givet was not entirely a figment of people's imaginations, as the first response of the French government to the threatening language of the Prussian king (and the movements to the Dutch border at Wesel of Prussian troops) had indeed been to erect such a camp, and to garrison it with a formidable military force (15,000 men). But these rumors had on 29 June elicited a threatening diplomatic note from the British government that had given France pause. For the moment the French pretended that the alleged military build-up was just intended to "train the troops" and the preparations actually had halted. But around the end of July the French Cabinet appears to have seriously discussed the plan to mount such a force. The minister of Foreign Affairs, Montmorin, and the minister for War, de Ségur, were in favor, but the Finance Minister
Brienne vetoed the plan, for lack of money. From that time on the Camp of Givet was nothing more than a French bluff to keep the Prussians and British guessing, and the Patriots hoping.
The reason why the British government was so alert to French military moves, was that the British Cabinet of Prime Minister William Pitt and Foreign Secretary Carmarthen had just in May fully endorsed the policy of active support of the "British" party (i.e. the Orangists) in the Republic, together with a campaign of subversion, espoused by Harris. Harris was of necessity (as Carmarthen offered little guidance) an envoy who not so much executed foreign policy, as made it. Ever since he arrived in the Dutch Republic at the end of 1784 he had immersed himself in its politics, and become the de facto leader of the Orangists. He had surrounded himself with agents of influence, like the Zeeland pensionaries Van de Spiegel and Van Citters, and other secret agents, like baron van Kinckel and count Charles Bentinck, who not only gathered intelligence, but actively took part in secret operations. At first his financial outlays had been relatively modest, on the same scale as those of his French colleague Vérac, but in May he had conceived a plan on a far larger scale. The immediate cause was that the Orangist States of Gelderland, who were financing the States Army troops that the States of Holland had tried to recall to the Holland borders in 1786, were now in severe financial difficulties, because of this unusual extra expense. Harris estimated that he needed £70,000 to support Gelderland. The Cabinet granted these funds, money to be laundered through the Civil list of king George with his grudging approval. It was clear that other expenses of the campaign of subversion also would be financed from this slush fund. Once he returned to the Republic Harris' agents swarmed out to bribe officers of several States Army regiments, paid by the States of Holland, to defect. The States were forced by their success to cashier a large number of officers whose loyalty was in doubt. This caused a tug of war with the other provinces in the States-General in June with parliamentary chicanes around the status of the delegations of the rival States of Utrecht determining temporary 4-3 majorities for either the Patriot or the Orangist side in the States General. Eventually there was a complete breach between the States of Holland and the majority of the States General (the provinces of Zeeland, Gelderland, Friesland and Utrecht (Amersfoort)) at the end of June In sum, Harris' efforts severely undermined the military power of the Patriot States of Holland, which might have shifted the balance of military power to the stadtholder, if it had come to a full-blown civil war. For that reason the States of Holland on 23 June (so before the incident at Goejanverwellesluis) passed a resolution asking for mediation between the warring parties in the Republic by France.