On the 8th of May Gustavus despatched his fleet, eight thousand strong, to Gotland. The command he gave to a German adventurer who has already figured in this story as Berent von Mehlen. This person, after breaking faith with his former master, Christiern, had married a cousin of Gustavus, and had become a trusted counsellor of the king. By what traits he became attractive in his monarch's eyes it is at this day difficult to conceive. Certainly as a general he knew as little as any general possibly could know. Again and again he had been given opportunity to display his warlike power, but thus far in every instance he had failed. He now set forth, as admiral of the Swedish fleet, to besiege the town of Visby. The siege began on the 19th of May, and was enlivened during a few weeks by several skirmishes. Nothing of importance, however, was accomplished. The siege was protracted through the summer, and at last the besiegers showed so little life that their leader, the favorite of Gustavus, was reported to have turned his coat once more and joined the enemy.[95]
Not yet had the siege begun when evidence was furnished that Fredrik was in league with Norby. So early as the 9th of May Gustavus wrote to Brask that the Danes were rumored to be supplying Norby with stores and ammunition. A few days later word arrived from Fredrik that he wished once more to put off the congress, this time till the 24th of June. Gustavus was now fairly mad with indignation, and declared to Brask that he would neither be present nor allow his envoys to be present at the proposed congress. He was discreet enough, however, to conceal his wrath from Fredrik; and, without refusing the offer of the Danish king, he called a meeting of his Cabinet, to which he urged Lubeck to send her envoys. Fredrik in the mean time had been negotiating on his own account with Norby, and had wrung promises from him which led to the impression that Norby had thrown up his allegiance to Christiern II. and was ready to accept the authority of Fredrik. Elated by this false hope, the Danish monarch felt in a position to ignore the slight that had been put upon him by Gustavus, and sent delegates, apparently unbidden, to the Swedish king and Cabinet, proposing that a congress be held in Denmark to settle all matters of dispute, the Swedish army in the mean time to withdraw from Gotland, and Norby to be given safe-conduct from the isle. These terms Gustavus rejected with disdain, declaring that he had striven for the good of all to scatter Norby with his "nest of robbers," and would consent to a meeting with Fredrik only on condition that in the interval Norby should receive no aid of any shape or kind. Fredrik, finding that Gustavus was determined, and that Norby's feigned alliance was somewhat airy, yielded reluctantly to this condition. The Swedish army continued in its camp at Visby; and the two monarchs, attended by their Cabinets, proceeded to the town of Malmö in hope of settling their disputes. The congress opened on the first day of September. The two monarchs with their retinues were present, together with envoys from the Hanseatic Towns. The meeting opened, as was usual, with an interchange of courtesies and with mutual promises to resist their common enemy, King Christiern. It was agreed, too, that all renegades from either country should be returned, and that citizens of one country should be entitled to any property belonging to them in the other. As soon, however, as the question of disputed territory arose, it became clear that no conclusion could be reached. It was therefore resolved, after long debate, that this question be postponed, to be decided by a congress of certain Hanse Towns, to be held in Lubeck in June of the following year. Till then a provisional frontier agreed upon by Norway, Denmark, and Sweden was to be observed; and Gotland was to remain during the interval in the hands of that party which held it on September 1. If it should be found that Norby held it on that day, he should be called upon to surrender it to Fredrik, to be placed by him under the temporary control of some person satisfactory to Sweden, Denmark, and Lubeck. If Sweden should continue the war in Gotland, she was to pay for all damage she might do. Either party by violating these terms was to become indebted to the other to the amount of one hundred thousand guilders. This conclusion reached, the congress was dissolved, envoys being first sent to Gotland to carry out the terms. Finding that Norby was still in possession, they entered into negotiations, and soon obtained a contract, signed by Norby as well as Mehlen, that each should withdraw his forces from the land.