What were the dates of the campaign that eventually led to the Treaty of Roskilde?
Treaty of Roskilde: The Treaty of Roskilde was concluded on 26 February (OS) or 8 March 1658 (NS) during the Second Northern War between Frederick III of Denmark–Norway and Charles X Gustav of Sweden in the Danish city of Roskilde. March Across the Belts:  The risky but vastly successful crossing was a crushing blow to Denmark, and led to the Treaty of Roskilde later that year, which handed Scania to Sweden.
i don't know