After a devastating defeat, Denmark–Norway was forced to give up a third of its territory to save the rest, the ceded lands comprising Blekinge, Bornholm, Bohuslän, Scania and Trøndelag, as well as Halland.

The Treaty of Copenhagen restored Bornholm to Denmark and Trøndelag to Norway in 1660, while the other provinces transferred in Roskilde remained Swedish.

As the Northern Wars progressed, Charles X Gustav of Sweden crossed the frozen straits from Jutland and occupied the Danish island of Zealand, with the invasion beginning on 11 February 1658.

At the Swedish Council held at Gottorp on 7 July, Charles X Gustav resolved to wipe his inconvenient rival from the map of Europe.

King Carl X Gustav was afraid that the Trønders would rise against their Swedish occupiers, and thought it wise to keep a large part of the men away.

[8] In the ninth article of the Treaty of Roskilde, which ceded Scania (Skåne), the inhabitants of the Scanian lands were assured of their privileges, old laws and customs.