Francis, Bishop of Wuertzburg, the bitter enemy of the Protestants, and the most zealous member of the League, was the first to feel the indignation of Gustavus Adolphus.  A few threats gained for the Swedes possession of his fortress of Koenigshofen, and with it the key of the whole province.  At the news of this rapid conquest, dismay seized all the Roman Catholic towns of the circle.  The Bishops of Wuertzburg and Bamberg trembled in their castles; they already saw their sees tottering, their churches profaned, and their religion degraded.  The malice of his enemies had circulated the most frightful representations of the persecuting spirit and the mode of warfare pursued by the Swedish king and his soldiers, which neither the repeated assurances of the king, nor the most splendid examples of humanity and toleration, ever entirely effaced.  Many feared to suffer at the hands of another what in similar circumstances they were conscious of inflicting themselves.  Many of the richest Roman Catholics hastened to secure by flight their property, their religion, and their persons, from the sanguinary fanaticism of the Swedes.  The bishop himself set the example.  In the midst of the alarm, which his bigoted zeal had caused, he abandoned his dominions, and fled to Paris, to excite, if possible, the French ministry against the common enemy of religion.

The further progress of Gustavus Adolphus in the ecclesiastical territories agreed with this brilliant commencement.  Schweinfurt, and soon afterward Wuertzburg, abandoned by their Imperial garrisons, surrendered; but Marienberg he was obliged to carry by storm.  In this place, which was believed to be impregnable, the enemy had collected a large store of provisions and ammunition, all of which fell into the hands of the Swedes.  The king found a valuable prize in the library of the Jesuits, which he sent to Upsal, while his soldiers found a still more agreeable one in the prelate’s well-filled cellars; his treasures the bishop had in good time removed.  The whole bishopric followed the example of the capital, and submitted to the Swedes.  The king compelled all the bishop’s subjects to swear allegiance to himself; and, in the absence of the lawful sovereign, appointed a regency, one-half of whose members were Protestants.  In every Roman Catholic town which Gustavus took, he opened the churches to the Protestant people, but without retaliating on the Papists the cruelties which they had practised on the former.  On such only as sword in hand refused to submit, were the fearful rights of war enforced; and for the occasional acts of violence committed by a few of the more lawless soldiers, in the blind rage of the first attack, their humane leader is not justly responsible.  Those who were peaceably disposed, or defenceless, were treated with mildness.  It was a sacred principle of Gustavus to spare the blood of his enemies, as well as that of his own troops.