The Northern War of 1655-60 was one of three wars that involved the majority of the Baltic powers of the time. In different historical traditions it is either the First Northern War (German, Russian, Scandinavia and British traditions) or the Second Northern War (Polish tradition). In the Polish tradition the Livonian War of 1558-83 was the First Northern War.
The Northern War of 1655-60 began as a Swedish attack on Poland-Lithuania, already at war with Russia and suffering from a Cossack revolt in the Ukraine. During the fighting Brandenburg and Denmark both entered the war and even Britain became involved. The war saw a dramatic collapse in Poland followed by an almost as dramatic revival.
Poland-Lithuania had been facing a Cossack revolt in the Ukraine since 1648. In 1654 the Cossacks signed a treaty with Muscovy that triggered the Thirteen Years War between Poland-Lithuania and Muscovy (1654-1667, with some gaps as we will see below). In 1654 the Russians had recaptured Smolensk, lost to them earlier in the century and in 1655 they advanced into Lithuania.
The Muscovite advance directly threatened Swedish interests around the Baltic. If it continued, Muscovy could soon control large parts of the Baltic coast. Sweden could have responded by supporting Poland-Lithuania, but there was a real danger that such a move would lead to a settlement between Poland-Lithuania and an alliance against Sweden (Just has would happen at the end of 1656). There was also a personal reason for attacking Poland. Charles X had only come to the Swedish throne in July 1654, after his cousin Christina abdicated. John II Casimir of Poland-Lithuania was the son of Sigismund III, who had briefly been king of Sweden before being deposed in 1599. Neither Sigismund nor John Casimir was willing to forget his claim to the Swedish throne.
The Polish Collapse
Charles’s initial aim was the conquest of Royal Prussia (west Prussia, part of the kingdom of Poland and including the important city of Danzig). In the summer of 1655 he launched a two pronged invasion of Royal Prussia. One army under Magnus de la Gardie was to attack from the Swedish possessions in Livonia, while the main army, at first under Arvid Wittenberg, would invade from Swedish Pomerania. Charles himself followed close behind with reinforcements.
Initial Polish resistance was almost non-existent. An army of 14,000 local levies was raised, but was unwilling to fight. An army of nearly 9,000 regular troops was to be raised, they were not ready in time. Wittenberg had 13,650 men, Charles another 12,700. The odds against the Poles were overwhelming. The response in northern Poland was totally unexpected. On 25 July at Ujście the palatinates of Poznań and Kalisz surrendered to Charles and promised to obey him as if he were the king of Poland.
A similar betrayal followed in Lithuania, where resistance to the Muscovites had been led by Janusz Radziwiłł, a political enemy of John Casimir. Radziwiłł felt that Lithuanian had been abandoned by the Poles, and so on 17 August he signed the treaty of Kiejdany, in which Lithuania accepted the protection of Charles. On 20 October a new treaty recognised Charles as Grand Duke of Lithuania, uniting Lithuania with Sweden.
John Casimir made a valiant attempt to restore the situation, but was defeated at Zarnów on 16 September. In the aftermath of the battle he left for exile in Silesia, while the Swedes advanced to occupy Cracow. For a short period most of Poland was under Swedish occupation.
The period of near uncontested Swedish dominance did not last long. Having fought in the later stages of the Thirty Years War on the Protestant side, Charles and his troops could not resist attacking the Catholic Church in Poland. Church property was looted, both officially and unofficially. Even as Swedish troops were reaching Cracow resistance was starting to emerge in the countryside.
The first serious military opposition came in Lithuania, where Radziwiłł lost the support of most of the army. In August 1655 the army formed a confederation at Wierzbolów under Pawel Sapieha. At the start of 1656 John Casimir returned to Poland and began to gather an army around him.
Charles spent the last months of 1655 attempting to conquer Royal Prussia, his original target. Here he was faced with a number of well defended cities, chief amongst them Danzig, and with a potentially dangerous enemy in Frederick William, elector of Brandenburg and Duke of Prussia. On 12 November, under pressure from John Casimir, the Royal Prussian nobility signed the treaty of Rinsk, in which Frederick William agreed to garrison the Prussian towns. Danzig, Elbing and Thorn refused to accept the garrisons, but in any case the agreement did not last long. With the apparent collapse of resistance in the rest of Poland, Elbing and Thorn surrendered to Charles. Frederick William withdrew his garrisons from the rest, and then on 17 January 1656 signed the Treaty of Königsberg with Charles, in which he switched his allegiance and that of Ducal Prussia from Poland to Sweden. Soon only Danzig was holding out against Charles.
Charles’s situation in the rest of Poland quickly deteriorated. His small garrisons were vulnerable the moment a sizable Polish army was in the field, and by the spring of 1656 John Casimir had close to 30,000 men at his disposal. Charles was forced to abandon his attempts to capture Danzig and return south to deal with the new threat. The move nearly led to disaster. Although he won a battle at Gołąb early in the year, he was then very nearly trapped at the junction of the San and Vistula rivers by almost the entire Polish army. He was able to escape, on the night of 5-6 April, but not without losing his artillery. On 29 June 1656 Warsaw was recaptured by the Poles.
Charles responded by forming a firmer alliance with Frederick William of Brandenburg. Their combined armies defeated the Poles at the battle of Warsaw (28-30 July 1656), but Charles was unable to take advantage of the victory. Frederick William was unwilling to advance much beyond the areas he had been promised by Charles and so Charles was forced to withdraw back to Royal Prussia, where Danzig was still holding out.
The international position now began to turn in Poland’s favour. Swedish success worried their neighbours and rivals. The Dutch responded by sending a fleet to break to blockade of Danzig. More seriously Tsar Alexis declared war on Sweden in May 1656 (Swedish-Muscovite War, 1656-61) and then made peace and formed an anti-Swedish coalition with Poland-Lithuanian (Treaty of Wilno, November 1656). This led to a Muscovite invasion of Livonia in the second half of 1656 that briefly threatened Riga.
The Swedes spent most of the rest of the war on the defensive. Despite the defeat at Warsaw, John Casimir was soon back on the offensive, defeating a join Swedish-Brandenburg army at Prostken on 8 October 1656. The Polish counter attack even reached into Brandenburg. In December a truce was agreed between Brandenburg and Poland-Lithuania. One more enemy was out of the war.
The war expanded again in 1657, bringing in the Empire, Transylvania and Denmark. On 6 December 1656 Charles signed the treaty of Radnot with George Rákóczi, prince of Transylvania, recognising him as king of Poland and grand duke of Lithuania. In January 1657 Rákóczi invaded Poland at the head of an army 25,000 strong. He was joined by Charles, and conducted a reasonably successful campaign in Poland, even capturing Warsaw in June 1657.
It was John Casimir who made the most effective foreign alliance. On 1 December 1656 he had agreed the Treaty of Vienna with the Emperor Ferdinand III. However, Ferdinand died in April 1657 and his successor, Leopold, was less sure about the wisdom of intervening in Poland-Lithuanian. However, the involvement of Rákóczi changed his mind. The Transylvanian Prince had ambitions in Hungary that directly threatened Leopold’s position, and so on 27 May 1657 he signed the Second Treaty of Vienna, in which he agreed to provide Poland with 12,000 troops. Austrian troops would garrison Cracow and Poznań.
The Imperial alliance had an even more valuable side-effect. It encouraged Frederick III of Denmark to declare war on Sweden in June 1657 (Swedish-Danish War, 1657-58). The initial Danish involvement was not to prove particularly effective, but it did force Charles to abandon the campaign in Poland to defend Sweden. Rákóczi was soon forced out of the war, his army destroyed by the Tatars. Frederick William of Brandenburg changed sides yet again (treaties of Wehlau, 19 September and Bromberg, 6 November) in return for recognition of his sovereignty in Ducal Prussia. The Polish period of the Northern War was all but over.
The Danish Phase
The Danes began aggressively. Twelve years earlier they had been forced to surrender the province of Jämtland and the island of Gotland to Sweden along with a thirty year lease on Halland (Treaty of Brömsebro, 1645). Now Danish armies in Scandinavia invaded Jämtland and Västergötland (north of Halland), while another force in Holstein invaded Swedish territory around Bremen.
Charles responded with an invasion of Denmark that reached the gates of Copenhagen. Advancing through Pomerania he entered Denmark through Holstein. While one army was sent west to restore the situation in Bremen, Charles captured the key Danish fortress of Fredriksodde, securing possession of Jutland. An attempt to defeat the Danish fleet produced an inconclusive battle at Møn. At the start of 1658 Charles looked to have stalled on Jutland.
Instead he took an astonishing risk, moving 5,000 across the ice to the island of Zealand. On 25 February this small Swedish army reached Copenhagen. Frederick III was shocked into a virtual surrender. At the treaty of Roskilde (8 March 1658) Denmark surrendered Scania, Bohuslän, Blekinge, Bornholm and Trondheim. It was a humiliating end to the war and saw Denmark expelled from the southern tip of Scandinavia.
The peace did not last long. Charles needed to keep his army occupied – he could not afford to disband it with the Poles now threatening to go onto the offensive, nor could he afford to keep it inactive in Sweden. Instead, he returned to Denmark, declaring war on the grounds that the Danes had not lived up to their obligations.
This second Swedish-Danish War (1658-60) did not go so well for Charles. By the end of August 1658 the Swedish army was once again outside Copenhagen, but this time the defences were ready. Charles was forced to settle into a siege. Worse was to come – the Danes had a treaty with the Dutch which required the Dutch to provide assistance if the Danes were attacked. This had not applied in 1657, when the Danes had been the aggressors, but in 1658 a Dutch fleet broke the Swedish naval blockade of Copenhagen. Soon it was Charles who was trapped on the Danish islands. During 1659 the remaining Swedish garrisons in Poland came under severe pressure, while Jutland was lost at the end of the year (battle of Nyborg, 24 November 1659).
Early in 1660 Charles died. Peace negotiations followed. The Peace of Oliva (3 May 1660) and the Peace of Copenhagen (6 June 1660) ended the war. The island of Bornholm was returned to Denmark, as was Trondheim, while the Swedes retained their conquests at the southern end of the Scandinavian Peninsula. Poland-Lithuania surrendered its claim to Livonia, while John Casimir finally abandoned his families claim to the Swedish throne (although kept the title of hereditary king of Sweden for his lifetime). The sovereignty of the elector of Brandenburg over Ducal Prussia was confirmed.
The end of the Northern War did not end the fighting. Both Sweden and Poland-Lithuania were still at war with Muscovy. The Swedish-Muscovite war ended in 1661, with a return to the situation before the war. The Thirteen Years War between Poland-Lithuania and Muscovy would drag on for another six years, not ending until 1667. The prolonged period of fighting saw Sweden and Brandenburg-Prussia make the most obvious gains. Muscovy had regained borderlands lost in earlier wars. Both Denmark and Poland-Lithuania came of the wars considerably weakened.