The Kalmar War (1611–1613) marked a significant conflict between Denmark–Norway and Sweden, with both nations vying for dominance over the Baltic Sea and its lucrative trade routes. The war began when Denmark-Norway, aiming to protect its control over the dominium maris baltici, declared war on Sweden following provocations by King Charles IX, who had sought alternative trade routes to avoid paying Denmark's Sound Dues. Charles IX went as far as to declare himself "King of the Lapps in Nordland" and began collecting taxes in traditionally Norwegian territories, even extending his claims south of Tromsø. Given that the Sound Dues were Denmark's main source of income, King Christian IV of Denmark-Norway saw this as a direct threat and, in April 1611, launched an invasion of Sweden.
Kalmar war was a conflict between Sweden and Denmark - the last before Sweden became a Great power. @ Lotroo
Denmark-Norway quickly gained the upper hand in the conflict, with Danish forces laying siege to Kalmar and eventually capturing it. Although Norwegian troops were stationed along the border, they were initially ordered not to advance into Sweden. In response, Swedish forces conducted raids, including the Storming of Kristianopel in June 1611. Meanwhile, Swedish troops under Baltzar Bäck invaded Norwegian territories in Jämtland and Härjedalen but faced strong resistance from the local population, leading to their eventual retreat in autumn 1612.
The war intensified following the death of Charles IX of Sweden in October 1611, when his son, Gustavus Adolphus, ascended to the throne. Although the new king initially sought peace, Christian IV saw an opportunity to press for a decisive victory and reinforced his armies in southern Sweden. The Danish-Norwegian forces captured the strategically important fortresses of Älvsborg and Gullberg in early 1612, cutting off Sweden's access to the western sea. Christian IV then attempted to launch a deep offensive into Sweden toward Stockholm, but harsh Swedish guerrilla tactics, scorched earth policies, and the desertion of unpaid mercenaries prevented the Danish army from advancing further.
By 1613, both sides were exhausted, and the pressures from external powers such as England and the Dutch Republic, who were invested in maintaining the balance of power in the Baltic trade, led to peace negotiations. The Treaty of Knäred, signed on January 20, 1613, marked the end of the war. Denmark-Norway emerged victorious, with Sweden agreeing to pay a hefty ransom for the fortresses of Älvsborg and Gullberg and surrounding territories, and Denmark-Norway successfully restored control over the trade routes through Lapland. However, Sweden secured a significant concession in gaining the right to free trade through the Sound Strait, exempting them from the Sound toll, which was a major blow to Denmark-Norway's economic interests.
In the aftermath, Denmark–Norway emerged as a recognized military power in Europe. However, because it did not achieve a complete victory, Sweden was able to recover under King Gustavus Adolphus. This recovery allowed Sweden to eventually challenge Denmark-Norway’s dominance in the Baltic region. The rivalry between the two powers continued and culminated in the Torstenson War (1643–1645), where Denmark-Norway was defeated and ceded control of the Baltic Sea to Sweden.
The Kalmar War also set the stage for a prolonged period of animosity between Norwegians and Swedes, influencing later historical events. After Denmark-Norway's defeat in the early 19th century, Norway resisted being ceded to Sweden under the Treaty of Kiel, leading to the Norwegian War of Independence. The resulting treaty allowed Norway to maintain a degree of sovereignty within a personal union with Sweden, which lasted until Norway gained full independence in 1905.
The Kalmar War signified Denmark-Norway's last successful defense of its dominium maris baltici against Sweden, drawing the attention of other European powers who opposed any single nation's dominance over the Baltic trade. This rivalry among maritime powers, including Great Britain, the Dutch Republic, and the Habsburgs, would play a significant role in the shifting dynamics of the region in the years that followed.