ritorial concessions, but Gustavus Adolphus' intervention in Germany was seen as a sign that the military power of Sweden was on the rise while Denmark's influence in the region was declining. Swedish armies invaded Jutland in 1643 and claimed Skåne in 1644. According to Geoffrey Parker, "The Swedish occupation caused a drop in agricultural production and a shortage of capital; harvest failure and plague ravaged the land between 1647 and 1651; Denmark's population fell by 20 per cent."
In the 1645 Treaty of Brømsebro, Denmark surrendered Halland, Gotland, the last parts of Danish Estonia, and several provinces in Norway. In 1657, king Frederick III declared war on Sweden and marched on Bremen-Verden. This led to a massive Danish defeat and the armies of King Charles X Gustav of Sweden conquered both Jutland, Funen and much of Zealand before signing the Peace of Roskilde in February 1658 which gave Sweden control of Skåne, Blekinge, Trøndelag and the island of Bornholm. Charles X Gustav quickly regretted not having destroyed Denmark completely and in August 1658 he began a two-year long siege of Copenhagen but failed to take the capital. In the following peace settlement, Denmark managed to maintain its independence and regain control of Trøndelag and Bornholm.
Denmark tried to regain control of Skåne in the Scanian War (1675–79) but this attempt was a failure. Following the Great Northern War (1700–21), Denmark managed to restore control of the parts of Schleswig and Holstein ruled by the house of Holstein-Gottorp in 1721 and 1773, respectively. In the Napoleonic Wars, Denmark originally tried to pursue a policy of neutrality and trade with both France and the United Kingdom and joined the League of Armed Neutrality with Russia, Sweden and Prussia. The British considered this a hostile act and attacked Copenhagen in both 1801 and 1807, in one case carrying off the Danish fleet, in the other, burning large parts of the Danish capital. This
