Pending these negotiations with Treves and France, the king's generals had entirely cleared the territory of Mentz of the Spanish garrisons, and Gustavus himself completed the conquest of this district by the capture of Kreutznach. To protect these conquests, the chancellor Oxenstiern was left with a division of the army upon the Middle Rhine, while the main body, under the king himself, began its march against the enemy in Franconia. The possession of this circle had, in the meantime, been disputed with variable success between Count Tilly and the Swedish General Horn, whom Gustavus had left there with 8,000 men; and the Bishopric of Bamberg, in particular, was at once the prize and the scene of their struggle. Called away to the Rhine by his other projects, the king had left to his general the chastisement of the bishop, whose perfidy had excited his indignation, and the activity of Horn justified the choice. In a short time, he subdued the greater part of the bishopric; and the capital itself, abandoned by its imperial garrison, was carried by storm. The banished bishop urgently demanded assistance from the Elector of Bavaria, who was at length persuaded to put an end to Tilly's inactivity. Fully empowered by his master's order to restore the bishop to his possessions, this general collected his troops, who were scattered over the Upper Palatinate, and with an army of 20,000 men advanced upon Bamberg. Firmly resolved to maintain his conquest even against this overwhelming force, Horn awaited the enemy within the walls of Bamberg; but was obliged to yield to the vanguard of Tilly what he had thought to be able to dispute with his whole army. A panic which suddenly seized his troops, and which no presence of mind of their general could check, opened the gates to the enemy, and it was with difficulty that the troops, baggage, and artillery were saved. The reconquest of Bamberg was the fruit of this victory; but Tilly, with all his activity, was unable to overtake the Swedish general, who retired in good order behind the Main. The king's appearance in Franconia, and his junction with Gustavus Horn at Kitzingen, put a stop to Tilly's conquests, and compelled him to provide for his own safety by a rapid retreat.