Sigismund advanced his troops towards Stångebro in Linköping where his sister Anna Vasa resided. On 8 September Charles executed a premature attack on Stångebro which was quickly repelled; his force was surrounded in the night and massacred by the Poles. Severed heads on lances and spikes startled Sigismund who ordered an end to the violence. The supposed truce did not come into effect, and, on the morning of 25 September, the armies clashed once more in a major engagement at the Battle of Stångebro. The prevailing fog was instrumental at hiding troop movement; the Swedish rebels used the opportunity to take the bridges on the river Stångån when Sigismund's men were falsely led into a truce and retreated to their camp. Their attempt to regroup and form a second defensive line proved futile and Charles emerged victorious as the Polish army was also cut off from supplies by superior Swedish warships.