The Dano-Swedish War of 1657–1658 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.
A harsh winter had forced the Dano-Norwegian fleet into port, and frozen the Great Belt and Little Belt straits. After entering Jutland from the south, a Swedish army of 7,000 battle-hardened veterans marched across the icy Little Belt onto the Danish island of Funen on 30 January 1658. The Swedes captured the island of Funen within a few days and then sent on to capture the islands of Langeland, Lolland, and Falster. The Swedish army continued to Zealand, threatening the Danish capital of Copenhagen.