In 1473, that zealous servant of Burgundy declared that if the burghers persisted in their refusal he would resort to force. Their reply was that Mulhouse could not take such an important step without consulting her friends, the Swiss. "Are the cantons going to help you pay your debts?" was the sneering comment of Hagenbach. "Mulhouse is a bad weed in a rose garden, a plant that must be extirpated. Its submission would make a charming pleasure ground out of the Sundgau, Alsace, and Breisgau. The duke knew no city which he would prefer to Mulhouse for a sojourn," were his further statements.[10]
Two days were given to the town council for an answer. Hagenbach remarked that it was useless to think that time could be gained until the mortgaged territories should return to Austria. "Far from planning redemption, Duke Sigismund is now preparing to cede to Charles le téméraire as much again of his domain and vassals." Still Mulhouse was not convinced that the only course open to her was to let Charles pay her debts and receive her homage. No answer was forthcoming in the two days, but ready scribes had prepared many copies of Hagenbach's letter, which were sent to all who might be interested in checking these proposals of Burgundy.
On February 24, 1473, a Swiss diet met at Lausanne and there the matter was weighed. Hagenbach's letter was shown to those who had not seen it, and methods of rescuing Mulhouse from her dilemma were carefully considered. Years ago a union had existed between the forest cantons and the Alsatian cities. There were propositions to renew this alliance so as to present a strong front to their Burgundian neighbour. The cantons had enough to do with their own affairs, but the result of the discussion was that, on March 14th, a ten-year Alsatian confederation was formed in imitation of the Swiss.
The chief members were Basel, Colmar, Mulhouse, Schlestadt, and two dioceses, and it is referred to as the Basse-Union or the Lower Union, the purposes being to guarantee mutually the rights of the contracting parties, to meet for discussion on various questions, and, specifically, to help Mulhouse pay her debts. A few days later, March 19th, there was a fresh proposition to make an alliance between this Basse-Union and the Swiss confederation. This required a referendum. Each Swiss delegate received a copy of the articles to take back to his constituents for their consideration. No bond between the confederation and the union was, however, in existence at the time when Charles was approaching Alsace. Various conciliatory measures on his part had somewhat lessened immediate opposition to him, but, nevertheless, there were frequent conferences about affairs. Diets were almost continuous and there were strenuous efforts to raise money to free Mulhouse from her hampering financial embarrassments.
Hagenbach had not followed up his threats of immediate war measures, but it was known that he had obtained imperial authorisation to assume the jurisdiction of Mulhouse, a step which her allies hoped to forestall by settling her debts. Strasburg offered to contribute six hundred florins, Berne and Soleure seven hundred, Basel four hundred, while Colmar, Schlestadt, Obernai, and Kaisersberg together hoped to raise another four hundred. A diet was called at Basel for December 11th, and Zürich and Lucerne were expected to enter into the union. The tidings of the duke's approach were undoubtedly a stimulus to these renewed efforts to make the league strong enough to withstand him. The sentiment expressed by the pious Knebel, "May God protect us from his mighty hand," voiced probably a wide-spread dread.
When Charles entered Alsace, his escort was large enough to inspire fear, but there was no opposition to his advance, though consultations, now at one city, now at another, were frequent. The duke paid little heed to their deliberations, under-estimating their importance, while he was gracious to any words of welcome offered to him. Strasburg sent him greetings while he rested at Châtenois, and so did Colmar. The latter town expressed her willingness to receive him and an escort of one or two hundred, but was firm in her refusal to admit a larger force within her walls. By this precaution, Charles was baffled in his plot to gain possession of the town, and so passed on his way.
On Christmas eve, the traveller made a formal entry into Brisac, where a temporary court was established, and where audience was given to various embassies with the customary Burgundian pomp. Meanwhile the troops, forced to camp without the walls, were a burden to the land, and seem to have been more odious than usual to their unwilling hosts.
The citizens of Brisac offered homage on their knees and had their hopes raised high by their suzerain's pleasant greeting, but they failed to obtain the hoped for assurance that the treaty of St. Omer should be observed in all respects. Among the envoys were many who undertook to remonstrate in a friendly fashion about the imposition of the "Bad Penny" tax on the Alsatians, and the over-severity of Hagenbach's administration. The cause of Mulhouse, too, was urged, notably by Berne. The representations of these last envoys were received most courteously. The duke rather thought that the city could be detached from the league, and therefore gave himself some trouble to establish friendly relations.
To Mulhouse, too, his tone was conciliatory. He wrote a pleasant letter to the town and despatched a councillor thither, who would, he assured them, arrange matters to their satisfaction. But an abortive coup d'état on the part of the Burgundians, which would have given them possession of Basel, destroyed the effect of these reassuring phrases. The burghers were warned in time, looked to their defences, and banished from their midst every individual suspected of Burgundian sympathies. Every newcomer was carefully scrutinised before he was admitted within the walls, and the Rhine was guarded most rigidly. The propriety of these precautions was soon proven.
Charles ordered a review at Ensisheim, the official capital of the landgraviate. Thither marched his troops from every quarter. Those from Säckingen, Lauffen, and Waldshut found their shortest route over the bridge at Basel, and there they appeared and begged to be allowed to cross. Their sincerity was doubted, and the least foothold on the city's territory was sternly refused then and a week later, when the request was renewed. The method of introducing friendly troops into a town and then seizing it by a sudden coup de main was what Charles had been suspected of plotting for Metz, and later for Colmar, and there seems to be no doubt that a third essay of this rather stupid stratagem was planned, only to fail again, and this time to be peculiarly disastrous in its reflex action.