Spinola, then entering the territory of Cleve, took session of Orsoy, an important place on the Rhine, besides Duren, Duisburg, Kaster, Greevenbroek and Berchem. Leaving garrisons in these places, he razed the fortifications of Mulheim, much to the joy of the Archbishop and his faithful subjects of Cologne, then crossed the Rhine at Rheinberg, and swooped down upon Wesel. This flourishing and prosperous city had formerly belonged to the Duchy of Cleve. Placed at the junction of the Rhine and Lippe and commanding both rivers, it had become both powerful and Protestant, and had set itself up as a free Imperial city, recognising its dukes no longer as sovereigns, but only as protectors. So fervent was it in the practice of the Reformed religion that it was called the Rhenish Geneva, the cradle of German Calvinism. So important was its preservation considered to the cause of Protestantism that the States-General had urged its authorities to accept from them a garrison. They refused. Had they complied, the city would have been saved, because it was the rule in this extraordinary campaign that the belligerents made war not upon each other, nor in each others territory, but against neutrals and upon neutral soil. The Catholic forces under Spinola or his lieutenants, meeting occasionally and accidentally with the Protestants under Maurice or his generals, exchanged no cannon shots or buffets, but only acts of courtesy; falling away each before the other, and each ceding to the other with extreme politeness the possession of towns which one had preceded the other in besieging.
The citizens of Wesel were amazed at being attacked, considering themselves as Imperial burghers. They regretted too late that they had refused a garrison from Maurice, which would have prevented Spinola from assailing them. They had now nothing for it but to surrender, which they did within three days. The principal condition of the capitulation was that when Julich should be given up by the States Wesel should be restored to its former position. Spinola then took and garrisoned the city of Xanten, but went no further. Having weakened his army sufficiently by the garrisons taken from it for the cities captured by him, he declined to make any demonstration upon the neighbouring and important towns of Emmerich and Rees. The Catholic commander falling back, the Protestant moved forward. Maurice seized both Emmerich and Rees, and placed garrisons within them, besides occupying Goch, Kranenburg, Gennip, and various places in the County of Mark. This closed the amicable campaign.
Spinola established himself and his forces near Wesel. The Prince encamped near Rees. The two armies were within two hours' march of each other. The Duke of Neuburg—for the Palatine had now succeeded on his father's death to the ancestral dukedom and to his share of the Condominium of the debateable provinces—now joined Spinola with an army of 4000 foot and 400 horse. The young Prince of Brandenburg came to Maurice with 800 cavalry and an infantry regiment of the Elector-Palatine.
Negotiations destined to be as spectral and fleeting as the campaign had been illusory now began. The whole Protestant world was aflame with indignation at the loss of Wesel. The States' government had already proposed to deposit Julich in the hands of a neutral power if the Archduke would abstain from military movements. But Albert, proud of his achievements in Aachen, refused to pause in his career. Let them make the deposit first, he said.
Both belligerents, being now satiated with such military glory as could flow from the capture of defenceless cities belonging to neutrals, agreed to hold conferences at Xanten. To this town, in the Duchy of Cleve, and midway between the rival camps, came Sir Henry Wotton and Sir Dudley Carleton, ambassadors of Great Britain; de Refuge and de Russy, the special and the resident ambassador of France at the Hague; Chancellor Peter Pecquius and Counsellor Visser, to represent the Archdukes; seven deputies from the United Provinces, three from the Elector of Cologne, three from Brandenburg, three from Neuburg, and two from the Elector-Palatine, as representative of the Protestant League.
In the earlier conferences the envoys of the Archduke and of the Elector of Cologne were left out, but they were informed daily of each step in the negotiation. The most important point at starting was thought to be to get rid of the 'Condominium.' There could be no harmony nor peace in joint possession. The whole territory should be cut provisionally in halves, and each possessory prince rule exclusively within the portion assigned to him. There might also be an exchange of domain between the two every six months. As for Wesel and Julich, they could remain respectively in the hands then holding them, or the fortifications of Julich might be dismantled and Wesel restored to the status quo. The latter alternative would have best suited the States, who were growing daily more irritated at seeing Wesel, that Protestant stronghold, with an exclusively Calvinistic population, in the hands of Catholics.
The Spanish ambassador at Brussels remonstrated, however, at the thought of restoring his precious conquest, obtained without loss of time, money, or blood, into the hands of heretics, at least before consultation with the government at Madrid and without full consent of the King.
"How important to your Majesty's affairs in Flanders," wrote Guadaleste to Philip, "is the acquisition of Wesel may be seen by the manifest grief of your enemies. They see with immense displeasure your royal ensigns planted on the most important place on the Rhine, and one which would become the chief military station for all the armies of Flanders to assemble in at any moment.
"As no acquisition could therefore be greater, so your Majesty should never be deprived of it without thorough consideration of the case. The Archduke fears, and so do his ministers, that if we refuse to restore Wesel, the United Provinces would break the truce. For my part I believe, and there are many who agree with me, that they would on the contrary be more inclined to stand by the truce, hoping to obtain by negotiation that which it must be obvious to them they cannot hope to capture by force. But let Wesel be at once restored. Let that be done which is so much desired by the United Provinces and other great enemies and rivals of your Majesty, and what security will there be that the same Provinces will not again attempt the same invasion? Is not the example of Julich fresh? And how much more important is Wesel! Julich was after all not situate on their frontiers, while Wesel lies at their principal gates. Your Majesty now sees the good and upright intentions of those Provinces and their friends. They have made a settlement between Brandenburg and Neuburg, not in order to breed concord but confusion between those two, not tranquillity for the country, but greater turbulence than ever before. Nor have they done this with any other thought than that the United Provinces might find new opportunities to derive the same profit from fresh tumults as they have already done so shamelessly from those which are past. After all I don't say that Wesel should never be restored, if circumstances require it, and if your Majesty, approving the Treaty of Xanten, should sanction the measure. But such a result should be reached only after full consultation with your Majesty, to whose glorious military exploits these splendid results are chiefly owing."
The treaty finally decided upon rejected the principle of alternate possession, and established a permanent division of the territory in dispute between Brandenburg and Neuburg.