Birger Jarl
There may have been additional reasons why the battle took place in 1247. The position of jarl in Sweden had passed from old Ulf Fase to his younger and more dynamic cousin Birger Jarl. Moreover, Holmger Knutsson had come of age, and, being a son of former king Canute II of Sweden, had his own aspirations to the throne. When Ulf Fase died, Birger Jarl may have felt it was time to deal with Holmger and his allies in Uppland.