Catherine Jagiellon, John III's wife, had proven to be a threat to the Swedish government since she was a Catholic and from the Polish–Lithuanian Commonwealth.

[5][6] Eric's royal army, which consisted of a few thousand,[3] besieged Åbo with all its "court ladies, monks, and dwarves".

The cannon fire from the royal army also heavily damaged the castle walls, leading to the defenders quickly being forced to surrender on August 12.

[7] The royal troops also plundered the already damaged Åbo, with more soldiers doing the same to gardens belonging to John III's family.

[3] A contemporary report from the time says that one of the royal officers, Anders Nilsson, received an order to murder John.