After a devastating defeat in the Second Northern War, King Frederick III of Denmark–Norway was forced to give up nearly half his Danish territory to Sweden to save the remainder.
Northern War of 1655–1660
The Northern War of 1655–1660 was fought between Sweden and the Polish–Lithuanian Commonwealth, with participation at different times by Russia, Brandenburg-Prussia, the Habsburg monarchy, and Denmark–Norway. It ended with the treaties of Copenhagen and Oliva in 1660.
Frederick III of Denmark
Frederick III was King of Denmark and Norway from 1648 until his death in 1670. He also governed under the name Frederik II as diocesan administrator of the Prince-Bishopric of Verden, and the Prince-Archbishopric of Bremen (1635–45).
Treaty of Roskilde
The Treaty of Roskilde was negotiated at Høje Taastrup Church and was concluded on 26 February (OS) or 8 March 1658 (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, Scania and Trøndelag, as well as Halland.