Thus stayed in his effort to win Louis's ear, Sigismund decided that he would make another essay towards a Burgundian alliance, this time face to face with the duke. On to Flanders he journeyed and found Charles in the midst of the ostentatious magnificence already described. Ordinary affairs of life were conducted with a splendour hardly attained by the emperor in the most pompous functions of his court. Sigismund was absolutely dazzled by the evidence of easy prosperity. The fact that a maiden was the duke's sole heiress led the Austrian to conceive the not unnatural idea that this attractive Burgundian wealth might be turned into the impoverished imperial coffers by a marriage between Mary of Burgundy and Maximilian, the emperor's son.
The visitor not only thought of this possibility, but he immediately broached it to Charles. The bait was swallowed. As to the main proposition which Sigismund had come expressly to make, that, too, was not rejected. The duke perceived that the transfer of the Rhenish lands to his jurisdiction might militate to his advantage. A passage would be opened towards the south for his troops without the need of demanding permission from any reluctant neighbour. The risk of trouble with the Swiss did not affect him when weighing the advantages of Sigismund's proffer, a proffer which he finally decided to accept. Probably he found his guest a pleasant party to a bargain, for not only did he broach the tempting alliance between Mary and Maximilian, but he, too, seems to have hinted that the title of "King of the Romans" might be added to the long list of appellations already signed by Charles.[6] As Sigismund was richer in kin, if not in coin, than the feeble Podiebrad, Charles gave serious heed to the suggestion which fell incidentally from his guest's lips, in the course of the long conversations held at Bruges.
Certain precautions were taken to protect Charles from being dragged into Swiss complications against his will, and then in May, 1469, the treaty of St. Omer was signed,[7] wherein the Duke of Burgundy accorded his protection to Sigismund of Austria and received from him all his seigniorial rights within certain specified territories.
The most important part of this cession comprised Upper Alsace and the county of Ferrette, but there were also many other fragments of territory and rights of seigniory involved, besides lordship over various Rhenish cities, such as Rheinfelden, Saeckingen, Lauffenburg, Waldshut and Brisac. This last named town commanded the route eastward, as Waldshut that to the southeast, and Thann the highway through the Vosges region.
Fifty thousand florins was the price for the property and the claims transferred from Sigismund to Charles. Ten thousand were to be paid at once, in order to ransom Waldshut from the Swiss. The remainder was due on September 24th. On his part, Sigismund specifically recognised the duke's right to redeem all domains nominally his but mortgaged for the time being, certain estates or seignorial rights having been thus alienated for 150 years.
This territorial transfer was not a sale. It was a mortgage, but a mortgage with possession to the mortgagee and further restricted by the provision that there could be no redemption unless the mortgager could repay at Besançon the whole loan plus all the outlay made by the mortgagee up to that date. Instalment payments were expressly ruled out. The entire sum intact was made obligatory. Therefore the danger of speedy redemption did not disquiet Charles. He knew the man he had to deal with. Sigismund's lack of foresight and his prodigality were notorious. There was faint chance that he could ever command the amount in question. Accordingly, Charles was fairly justified in counting the mortgaged territory as annexed to Burgundy in perpetuity.
Sigismund pocketed his florins eagerly. Nothing could have been more welcome to him. But this relief from the pressure of his pecuniary embarrassment did not inspire him with love for the man who held his lost lands. His sentiments towards Charles were very similar to those of an heir towards a usurer who has helped him in a temporary strait by mulcting him of his natural rights.
As for the emperor, when this transfer of territory was an accomplished fact, he began to take fright at the consequences. He did not like this intrusion of a powerful French peer into the imperial circle.[8] At the same time he was ready to make him share responsibility in any further difficulties that might arise between Sigismund and the Swiss.