The First Northern War opened with the invasion of northern Poland by King Charles X of Sweden after Polish king John II refused an alliance with Sweden against the encroaching Muscovites and Cossacks. At war’s end, Sweden reached its greatest extent as an imperial nation.

Charles X Charles X Gustav , the field commander of Sweden’s armies in the last phases of the Thirty Years’ War, ascended to the throne of Sweden upon the abdication of Queen Christina on June 6, 1654. In January of that same year, the war of the Polish-Lithuanian Commonwealth against a Cossack uprising entered a new chapter when Cossack leader Bohdan Khmelnytsky Khmelnytsky, Bohdan signed an alliance with the Russian czar Alexis Alexis . [kw]First Northern War (July 10, 1655-June 21, 1661)
[kw]War, First Northern (July 10, 1655-June 21, 1661)
[kw]Northern War, First (July 10, 1655-June 21, 1661)
Wars, uprisings, and civil unrest;July 10, 1655-June 21, 1661: First Northern War[1850]
Sweden;July 10, 1655-June 21, 1661: First Northern War[1850]
Denmark;July 10, 1655-June 21, 1661: First Northern War[1850]
Poland;July 10, 1655-June 21, 1661: First Northern War[1850]
Livonia;July 10, 1655-June 21, 1661: First Northern War[1850]
Northern War, First (1655-1661)

That summer, 100,000 Muscovites and Cossacks drove deep into Lithuanian territory, taking Smolensk. Charles, who was anxious both to protect Swedish territory in Livonia and to build up Swedish military strength, approached Poland’s John II Casimir Vasa John II Casimir Vasa with the offer of an alliance. Charles required Polish coastal territories and John’s renunciation of his dynastic claim to Sweden’s throne in return for his aid. When John refused his terms, Charles decided to attack northern Poland and carve out his own territory. Sweden;war with Poland

On July 10, 1655, 50,000 men and 72 cannon moved into Poland from Pomerania, while a Swedish army crossed into Lithuania from Livonia. Aside from well-defended Gdansk, Polish resistance collapsed. Charles himself led an expedition of 50,000 men from Sweden in August. Lithuanian nobleman Janusz Radziwill Radziwill, Janusz signed a treaty with Sweden in August, which was to align Lithuania with Sweden, and a second treaty on October 20, in which Charles assumed the title grand duke of Lithuania. Warsaw fell on September 8 and Kraków on October 19, and John fled west. In January, 1656, Sweden settled Brandenburg-Prussia’s claims to East Prussian cities, ceding them as Swedish fiefs in the Treaty of Königsberg Königsberg, Treaty of (1656) .

Swedish maltreatment of the Poles quickly kindled resentment and resistance, as did Radziwill’s arrangements with Charles. By the spring of 1656, John was possessed of a considerable—and growing—army. Sweden’s successes also alarmed Russia, Denmark, and Brandenburg, who formed a rough axis against Sweden. In March, Charles marched on Lwów but was forced back, narrowly escaping a trap in which he lost his artillery and baggage. Charles bought off Frederick William Frederick William, the Great Elector , the Great Elector, in the Treaty of Marienburg Marienburg, Treaty of (1656) (Malbork) of June 25, ceding him rights to captured Baltic Polish towns in return for 8,000 troops. John retook Warsaw on June 29 but lost it a month later in the wake of the Battle of Warsaw, Warsaw, Battle of (1656) which saw 18,000 Swedes and Brandenburgers defeat 40,000 Poles (July). Both sides utilized a preponderance of cavalry, reflecting the influence of the steppe tradition and demonstrating Charles’s adaptability as a military leader.

To the north, Alexis attacked Swedish Livonia with an army of 35,000 men in the summer, but the offensive was broken on well-defended Riga, a setback that took Russia out of the war with the signing of a three-year armistice. Renewed Polish pressure forced the Swedes and Brandenburgers back into Prussia in the fall of 1656. Poland signed an armistice with Russia in October and received aid from Austria through the Treaty of Vienna Vienna, Treaty of (1656) on December 1. Charles had ceded all his rights and claims in Prussia to Frederick William for more troops and enlisted the support of Transylvanian prince György Rákóczi Rákóczi, György II , whom he promised the Polish throne.

In early 1657, the Swedes and Brandenburgers drove far into central Polish territory. This prompted the Danes to move against Swedish-held east central Norway and Bremen. Though meeting powerful resistance in Poland, Charles pulled out 13,000 troops and marched them against Denmark. All but abandoned by his erstwhile ally, Frederick William joined with the Poles and Austrians in the Treaty of Wehlau Wehlau, Treaty of (1657) (Znamensk) in September, 1657, effectively ending the Polish phase of the war. Charles’s army invaded Denmark, but was then stymied by a lack of naval power that would have allowed needed island hopping. The dead of winter, however, allowed a bold march over frozen waterways. The startled Danes then sued for peace and signed the humiliating Treaty of Roskilde (1658) Roskilde, Treaty of (1658) . Frederick III Frederick III (king of Denmark and Norway) surrendered Scania, Halland, Blekinge, a number of strategic islands, and Trondheim in central Norway; all told, Denmark lost about half of its territory.

Lacking other viable options, Charles mounted another attack on Denmark in August, 1658, perhaps seeking to destroy the country entirely. In this second Danish war, the Swedes marched to Copenhagen and besieged the city. Dutch naval aid broke the Swedish blockade and supplied the city, while an allied army led by Brandenburg attacked Holstein and moved north, trapping the Swedes around Copenhagen. An all-out assault on Copenhagen in February, 1659, failed, and Charles was defeated at Nyborg Nyborg, Battle of (1659) on the Island of Fyn in November, as he was seeking to retreat westward.

Farther east, Frederick William’s troops occupied Swedish Pomerania. Undaunted, Charles was planning an assault on Norway when he met his untimely death in Göteborg on February 13, 1660. Negotiations for peace proceeded rapidly.

Three treaties ended the wars that were set off by Charles. The Treaty of Oliva (May 3, 1660) Oliva, Treaty of (1660) , signed by Sweden, Poland, Brandenburg-Prussia, and Austria, overshadowed by the French, guaranteed to Sweden territories on the southern Baltic except Kurland. John gave up his claims to the Swedish throne and relinquished Livonia to Sweden, while all parties recognized Frederick William’s control of East Prussia. With the Treaty of Copenhagen (June, 1660) Copenhagen, Treaty of (1660) , Sweden and Denmark affirmed most of Charles’s gains, though he lost Trondheim and Bornholm. Russia and Sweden ended hostilities by signing the Treaty of Kardis Kardis, Treaty of (1661) on June 21, 1661.

With the war, Sweden reached its greatest extent as an imperial nation. The victorious allies hemmed in the country but did not defeat it. By leaving his four-year-old son as his heir (Charles XI), Charles ensured several decades of peace. It would be another four decades before Sweden again set out on such an aggressive campaign. In fact, Sweden drifted into France’s camp as a counterweight to rapidly developing Brandenburg-Prussia.

For his part, Frederick William proved the wisdom of a flexible attitude to alliances, and he won East Prussia in the bargain. The war saw Brandenburg’s army increase from 1,800 to 22,000 troops, and its generals learned much from their Swedish allies. This proved to be the birth of the Prussian military state, with enormous consequences for European history. Frederick William’s growing absolutism was mirrored by that of Frederick III, Frederick III (elector of Brandenburg) who gained broad and unfettered powers to modernize and defend a humbled Denmark largely at the expense of the nobility.

Poland emerged badly battered and still at war with Russia. Along with John’s claim to Sweden’s throne, Poland lost its orientation to the Baltic. Much, however, remained unchanged. European diplomats still believed that military victories had to be recognized and rewarded, but they tempered their generosity with a growing conviction that naked aggression, like the aggression of Charles X, had to be discouraged.

• Frost, Robert I. After the Deluge: Poland-Lithuania and the Second Northern War, 1655-1660. New York: Cambridge University Press, 1993. A detailed chronological narrative and analysis of the political and military aspects of the Polish phase of the war.
• Frost, Robert I. The Northern Wars, 1558-1721. New York: Longman, 2000. Discusses the Northern Wars in the broad context of the early national struggles for dominance in the Baltic region, integrating political, diplomatic, and military matters.
• Kirby, David. Northern Europe in the Early Modern Period: The Baltic World, 1492-1772. London: Longman, 1990. Examines Sweden’s role as a major political power, and the country’s eventual decline. Discusses the evolving political and social systems of the Baltic states.
• Lockhart, Paul D. Sweden in the Seventeenth Century. New York: Palgrave, 2004. Lockhart briefly discusses, in detail, the war as an outgrowth of the reign and ambitions of Charles X.
• Nordstrom, Byron. The History of Sweden. Westport, Conn.: Greenwood Press, 2002. The place to begin for the reader who wants a broad overview of the country’s history.
• Oakley, Stewart P. War and Peace in the Baltic, 1560-1790. New York: Routledge, 1992. This work provides a brief but useful overview of the war from an international perspective.

Alexis; Charles X Gustav; Christina; Frederick William, the Great Elector; Gustavus II Adolphus; John III Sobieski; Leopold I; Axel Oxenstierna; Lennart Torstenson. Northern War, First (1655-1661)