The Dano-Swedish War of 1658–1660 was a war between Denmark–Norway and Sweden, with the former backed by the Dutch Republic and Poland. It is known in Denmark as the Second Karl Gustav War (Danish: Anden Karl Gustav-krig), in Norway as Bjelkes Feud (Norwegian: Bjelkefeiden) in Sweden as Karl Gustav's Second Danish War (Swedish: Karl Gustavs andra danska krig), and in the Netherlands as the Swedish-Dutch War (Dutch: Zweeds-Nederlandse Oorlog).
It was a continuation of an earlier conflict between the two belligerents which had ended just months earlier, after Sweden and Denmark brokered a peace agreement in Roskilde in 1658. In the aftermath of that conflict, the Swedish king Charles X Gustav desired to add the province of Royal Prussia in Poland to the Swedish realm, but his position in the region was not strong enough with the opposition of Brandenburg and Austria. However, the Danes stalled and prolonged the fulfillment of some provisions of the earlier peace; the Swedish king decided to use this as a pretext to attack with an ambitious goal: to vanquish Denmark as a sovereign state and raze the capital of Copenhagen. A quick and decisive defeat of Denmark was however only seen as a means to a greater end. The long-term goal was to wage war in Europe without fearing Danish interference.
The Swedish army surrounded Copenhagen, hoping to starve it into submission. This failed when the Dutch Republic joined the conflict on the Danish side and a reinforcing fleet managed to smash its way through the Swedish naval forces in Øresund. Charles then tried a decisive assault on the city, hoping to conquer it and win the war; this plan likewise failed. Brandenburg, Poland and Austria then also joined the war against the Swedes.
Charles X fell ill in early 1660 and died in February of that year. With the death of the Swedish king, one of the major obstacles to peace was gone and the Treaty of Oliva was signed with the Allies (Poland, Austria and Brandenburg). However, the Danes were not keen on peace after their recent successes and witnessing the weakness of the Swedish efforts. The Dutch retracted their blockade, but were soon convinced by the Danes to support them again. The French and English intervened for the Swedish and the situation was again teetering on the edge of a major conflict. However, the Danish statesman Hannibal Sehested negotiated a peace treaty without any direct involvement by foreign powers and the conflict was resolved with the Treaty of Copenhagen, where Sweden was forced to return Bornholm to Denmark and Trøndelag to Norway. The treaty of 1660 established political borders between Denmark, Sweden and Norway which have lasted to the present day.
Background
Charles X of Sweden had concluded the earlier war with Denmark with a stunning victory by succeeding in the bold March across the Belts. Denmark-Norway had been forced into a humiliating peace in the Treaty of Roskilde in which Denmark had to cede Scania, Halland and Blekinge on the Scandinavian Peninsula and the island of Bornholm, and Norway lost the provinces of Båhuslen and Trøndelag. Europe was stunned by the quick victory, and Charles proudly publicized his accomplishments. However, peace meant new problems. In the peace treaty of Roskilde, Denmark was obliged to supply the Swedish army with provisions until May 1658, but soon thereafter the army would need to be moved. The Swedish king knew that the army would not be able to be supplied in Sweden for long, and disbanding it was not desirable with the Poles eager to revenge the 1655 invasion of Poland-Lithuania. Sweden was not in want of enemies to attack: campaigns in Livonia and Estonia were considered, but were rejected due to supply problems. The Swedish King maintained that his main goal was to invade Royal Prussia, but he also wanted to punish Frederick William of Brandenburg-Prussia. The many enemies in continental Europe, among them Poland and a hostile Dutch would make this a difficult endeavor however. A new attack on Prussia would also see little international support, France was already urging peace. The surprising Swedish solution to this dilemma would be to return to Denmark in an attempt to finish the job.
When the Danish stalled and prolonged the fulfillment of some provisions of the earlier peace treaty the Swedish king decided to use this as a pretext to attack with a breathtaking goal: to vanquish Denmark as a sovereign state, raze the capital of Copenhagen and divide the country into four administrative regions. This would allow Sweden to control the Baltic Sea and bring in large customs revenues. However, even this ambitious goal was just to be stepping stone towards the ultimate plan of a quick conquest of Denmark so that the Swedes could wage a campaign in Europe without risking Danish interference.
Events
In June 1658 it was decided that the Swedish forces would attack. On August 6, 1658 a fleet of 70 ships with 5,700 men and 18 pieces of light artillery embarked upon a journey to Denmark. Since the previous war, Jutland was still occupied by Swedish troops and there were troops on Fyn. In addition to this, Field Marshal Gustav Otto Stenbock had assembled reinforcements in Scania in Southern Sweden. The plan was for the Swedish army to march on Copenhagen.
Siege of Copenhagen
On August 11, 1658 Charles X and his forces reached Valby hill (current day Frederiksberg) from where they could overlook the Danish capital. His arrival was expected and Danish King Frederick III had already ordered every building outside the city walls burnt, even though it had housed a third of the population of the city. That same day the city gates were closed and would not open again for another 22 months. A Swedish fleet of 28 ships blocked the harbor, preventing resupply by sea. The siege had begun.
When the Swedish king arrived to find half the city in flames and the Danes willing to put up a fight he had a difficult decision to make, whether to press forward immediately or whether to lay siege on the city and try to starve it out. His advisers were divided on the issue, and the king ultimately decided on the latter route. The wisdom of this decision has been questioned, since the Danish defenses were in poor shape initially. However, the population of Copenhagen rallied behind Frederick III, and the walls, moats and other defensive structures of the city were quickly improved. A large number of cannons were brought into the city from ships anchored in the harbor and placed along likely attack routes. The city also had plenty of defensive materiel: 50 tonnes (110,000 lb) of lead, 4,000 muskets, and a staggering 810 kilometres (500 mi) of slow match.
The Swedish siege force consisted of 11 brigades and 16 squadrons comprising 4,000 infantry, 2,000 cavalry and 50 cannons. The Swedes took the outer defensive perimeter, built in 1625 by Christian IV, which had fallen into disrepair. It was hastily repaired and artillery was brought to bear on the city. The Danes would not let the Swedish attack go uncontested, and made several counter-attacks. On August 23, 1658 almost 3,000 students, sailors and soldiers staged a surprise sortie through a hidden passage in the wall, destroying fortifications under construction and capturing three cannons.
Over 200 heated shot a day were hurled into the city, and several large howitzers were brought to bombard the Danish capital, including the 300-pounder "Eric Hansson", earlier used in the siege of Kraków. But the citizens of Copenhagen proved to be resilient and endured the constant barrage.
Kronborg captured
In a 1649 treaty the Dutch had pledged to defend Denmark against unprovoked aggression, and from a Swedish point of view it was essential to establish naval supremacy in Øresund to keep the Dutch out should they decide to intervene in the conflict. Kronborg Castle sat near the narrowest part of Øresund, a sound only four kilometres wide, which gave the castle a supreme strategic importance. Frederick III had appointed the colonel Poul Beenfeldt commander of the castle and ordered him to defend it at all costs. Should he fail in that, Kronborg was to be blown up to prevent the Swedes from using it.
On August 16 the Swedes arrived at Helsingør, took shelter in the city and started bombarding the castle with artillery. The Danes returned the fire, attempting to set the city on fire. They managed to destroy a dozen houses, but the fire did not spread enough to cause a conflagration. Danish artillery rained continually on the Swedish soldiers. However, the Swedish force still managed to advance, taking the outer line of defenses. The mood in the castle darkened, and Beenfeldt's courage wavered. The Lord High Admiral of Sweden, Carl Gustaf Wrangel, resorted to subterfuge and spread the rumor that Copenhagen had fallen and the Swedish soldiers started a false celebration. Discouraged and demoralized, the Danes capitulated. The loss of Kronborg was a blow for the Danish; 77 captured cannons were quickly put to use in the siege and with the castle in Swedish hands, it was believed that the Dutch would have a difficult time to come to aid.
Battle of the Sound
Despite Swedish hopes that the Dutch would not enter the conflict, they honored their 1649 treaty by sending a 45-ship relief fleet. On October 7, 1658 the Dutch fleet set sail from Vlie. Two weeks later, on October 22, it anchored northwest of Helsingør, unable to proceed for six days due to wind conditions. Wrangel suggested the Swedes should attack, but Charles X still wanted to avoid provoking the Dutch.
On October 29 at eight o'clock in the morning, a shot was heard from the Dutch flagship. It was the signal to advance and smash the Swedish line. The Dutch fleet was divided into three squadrons. Vice Admiral Witte de With on the 54-gun ship Brederod and his 11-ship squadron led the charge, followed by Admiral Jacob van Wassenaer Obdam on the 72-gun Eendracht with 13 ships in the squadron. The last squadron, led by Pieter Floriszoon had 11 ships. In total, the Dutch fleet consisted of 45 ships with 1,838 cannons and 4,000 sailors. Following the warships, many transports with large quantities of food and supplies as well as 28 regiments of experienced soldiers followed, in total 2 300 men. Standing against them was a Swedish navy force led by Carl Gustaf Wrangel and Admiral Klas Hansson Bjelkenstjerna, consisting of 43 ships, with 1,605 cannons and 4,055 sailors. The Swedes also had great hopes that the coastal artillery of Kronborg would inflict great damage. Charles personally fired the first hostile shot from Kronborg, but it fell short; the Dutch had wisely chosen to sail closer to the Swedish side, where there were fewer land-based guns to contend with. The Swedish force had more guns, but the Dutch had the advantage of the wind. In the narrow straits of Øresund, nearly a hundred warships now battled.
The engagement was confusing for both sides, and the view was soon obscured by gunpowder smoke. Many ships on both sides were badly damaged, and around 2,000 men killed or wounded. Towards the end, a squadron of Danish ships met up with Dutch and escorted them into the harbor of Copenhagen. The Swedish fleet had failed; much-needed reinforcements and supplies had reached the beleaguered Danish town. The combined Danish and Dutch fleet now had control of the seas, forcing the Swedish fleet to seek refuge in the harbor of Landskrona on the Swedish mainland.
Attack on Copenhagen
After six months of siege the Dutch had re-opened the sea lanes. Charles now faced a difficult choice: if he tried to sue for peace, the conditions would have been worse than the previous peace. The other option was an all-out attack on Copenhagen, hoping that conquering the city would end the war. The number of Swedish attackers is somewhat uncertain, roughly 8,000 men, comprising 4,500 infantry, 2,000 cavalry, 1,000 sailors and a few hundred gunners. The king planned the attack meticulously, but neglected to uphold adequate secrecy; the Danes were soon fully aware of the details of the Swedish attack plan thanks to a number of deserters and spies able to move between the encampments. The Danes had 6,000 trained soldiers, and an additional 5,000 men and women from the city had also taken up weapons, bringing the number of defenders to 11,000.
The Swedish forces had performed diversionary attacks on the outskirts of the city on two consecutive nights in order to tire the defenders, and at midnight on February 11, 1659, the main attack commenced. The main spearhead of the Swedish forces attacked from south of St. Jørgens lake with the King himself in overall command. A hundred cannons on Slotsholmen were brought to bear on the Swedish attackers with fast and accurate fire. The two attacking divisions advanced nevertheless, led by major general Fabian von Fersen and major general Johan von Essen. They reached the outer palisades on the ice, which were quickly breached, but the Swedes were immediately stopped by holes in the ice that the Danes had cut. The bridges they had brought were not long enough after the ice moats had been widened with the help of Dutch marines. Caught on the ice, the Swedes were in the open and subject to heavy fire. Longer bridges were eventually brought, and the attack continued towards the city walls. The battle was ferocious, with the attackers desperately trying to establish a bridgehead on the walls. But in the end, the defenders were successful and the Swedes were thrown back.
The northern attack force moved south towards Østerport where the fortification Kastellet laid. The Swedes got very close to Nyboder and were in the process of crossing the moat, when they fell victim to a well-conducted ambush, and withdrew with heavy losses. Around 6 in the morning, Charles X of Sweden knew that all attacks had failed. He ordered a retreat to the outskirts of the city, back to the starting position.
The victory was important for the Danes. Not only had their arch-enemy been defeated, out of the smoldering city came a stronger bourgeoisie with renewed confidence, more privileges and an improved position vis-a-vis the Danish crown. In many ways, it was a new Denmark which emerged from the assault of its capital on February 12, 1659.