During the summer of 1198, which for a long time afterward was called the Bergen-summer, there was continual skirmishing in and about Bergen. On the night after August 10th the Baglers, led by Bishop Nicholas, rowed up to the landings with two ships full of wood. At the bishop's command they set fire to the town in three different places, and soon the greater part of it, including six churches, was laid in ashes. The Birchlegs had all they could do to save the wooden citadel (_Sverre's Borg_). The inhabitants of Bergen could never afterward forgive Bishop Nicholas and his party for the loss they suffered by this fire; but as heartily as they had heretofore hated the Birchlegs they now hated the Baglers. Sverre found his position untenable after the town had been burned, and proceeded with his men overland to Throndhjem. Meanwhile the Baglers, who had many ships, were masters on the coasts. Many deserted the king and supported the Baglers; but there were also some of their men who went over to Sverre. Among the latter was Thorstein Kugad, who had surrendered his garrison in Nidaros, and who now returned to Sverre and begged his pardon. This was given, and Thorstein became one of Sverre's useful men. King Sverre spent the winter 1198-99 in Nidaros. His position was a desperate one. Outside of the Throndhjem country he had very little power, and the Baglers were masters at sea. Then, furthermore, a terrible blow was dealt Sverre, as Pope Innocent III., in October, 1198, issued his bull declaring Sverre to be in the ban of the Church, and laying the whole country under interdict, closing all churches and forbidding the administration of the sacraments wherever the people acknowledged King Sverre. It is easily understood what horror such a papal bull would create at that time. Sverre did not lose courage, however, but called the Throndhjem people together and asked them to help him. They showed their usual loyalty, and with their help he set to work to build a new, strong fleet and to improve the fortifications of the town. In the spring the Baglers appeared in the Throndhjem Fjord with a strong fleet, and, after some skirmishing, the two fleets met in battle at Strindsö, June 18, 1199. It was a desperate fight, where no quarter was given. The result was a victory for King Sverre and the Birchlegs, who returned to town with most of the enemy's ships. The prisoners taken on this occasion were nearly all slain. Bishop Nicholas, who watched the beginning of the battle from a safe distance, fled with his ship when he saw that the Baglers were losing, and Sigurd Jarlson and Reidar the Messenger followed his example.