 The ice was thick, and the work was done in heavy snowfall from 4 o'clock in the afternoon till evening on the 10 February.Spies reported that the Swedish army had moved from their camp, Carlstad, at Brønshøj and had taken up positions behind Valby Hill, and when the Swedes began their assault about midnight the same evening, they met heavy resistance.The main assaults were made against Christianshavn and Vestervold, but the chopped-up ice and the massed weaponry on the wall made the densely packed attackers pay a horrific toll in lives.