Several prominent opponents of Sverre, including bishop Nikolas Arnesson of Oslo, who had been a halfbrother of King Inge I of Norway and exiled archbishop Erik Ivarsson met at the marketplace of Halör in Skåne, then part of Denmark.

The war between the Bagler, with the open support of the Church, and the Birkebeiner, was to last for the rest of the reign of King Sverre.

The Baglers established themselves in the Viken area, which was both the bishopric of Nikolas Arnesson and the former power base of King Magnus V. On 18 June 1199, the two fleets met at the naval Battle of Strindafjord (Slaget på Strindfjorden).

After these two parties were reconciled in 1217, a more ordered system of government centered around the king was gradually able to bring an end to the frequent risings.

The background for these conflicts were the unclear Norwegian succession laws, social conditions and the struggle between Church and King.