The Dano-Swedish War of 1657–1658, known in Denmark as the First Karl Gustav War in Norway as Krabbes Feud and in Sweden as Karl Gustav's First Danish War, was a conflict between Sweden and Denmark–Norway during the Second Northern War. In 1657, Charles X of Sweden and his Swedish army were bogged down in Poland. Frederick III of Denmark-Norway saw an opportunity to recover the territories lost in 1645 and attacked Sweden. The outbreak of war with Denmark provided Charles with an excuse to withdraw from the Polish campaign and move against Denmark.

The Treaty of Roskilde was negotiated at Høje Taastrup Church and signed (NS) during the Second Northern War between Frederick III of Denmark–Norway and Karl X Gustav of Sweden in the Danish city of Roskilde. 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 (Båhuslen), Scania (Skåne) and Trøndelag, as well as her claims to Halland.