He therefore selected a place which Gustavus could not abandon, and so would be obliged to leave Bavaria garrisoned only by a force insufficient to withstand the attacks of Pappenheim, who had collected a considerable army for the recovery of the territories of Maximilian.
Such a point was Nuremberg, the greatest and strongest of the free cities, and which had been the first to open its gates to Gustavus.

The Swedish king could hardly abandon this friendly city to the assaults of the Imperialists, and indeed its fall would have been followed by the general defection from his cause of all that part of Germany, and he would have found himself isolated and cut off from the North.
As soon as Gustavus perceived that Nuremberg was the point towards which Wallenstein was moving, he hastened at once from Munich to the assistance of the threatened city.

The forces at his disposal had been weakened by the despatch of Marshal Horn to the Lower Palatinate, and by the garrisons left in the Bavarian cities, and he had but 17,000 men disposable to meet the 60,000 with whom Wallenstein was advancing.

He did not hesitate, however, but sent off messengers at once to direct the corps in Swabia under General Banner, Prince William of Weimar, and General Ruthven, to join him, if possible, before Nuremberg.
Marching with all haste he arrived at Nuremberg before Wallenstein reached it, and prepared at once for the defence of the city.

He first called together the principal citizens of Nuremberg and explained to them his position.