Sverre happened to be in Viken, and the two forces soon encountered each other, although no major battles were fought. Sverre gave his eldest son, Sigurd Lavard, the responsibility of guarding a ballista he had had built. However, the Baglers launched a surprise night attack during which the ballista was destroyed and Sigurd and his men were chased away. Sverre was furious and never gave his son a command again. After some more indecisive fighting, Sverre sailed north to Trondheim, where he spent the winter. The Baglers had Inge hailed as king on Borgarting and soon established a firm control over the Viken region, with Oslo as their main seat.