In autumn 1186, the Kuvlungs attacked Nidaros. This offensive took Sverre by surprise; he took refuge in the recently constructed stone castle Sion. The Kuvlungs, unable to take the castle, were forced to retreat. In 1188 Sverre sailed south with a large fleet. They first met at Tønsberg, but neither side dared to offer battle. The Kuvlungs slipped away to Bergen. Sverre attacked Bergen just before Christmas. Jon Kuvlung was killed, which ended the Kuvlung rising. Some minor uprisings followed, but these never rose above banditry and were suppressed on a local scale.