Christian IV from the Oldenburg dynasty, who ruled Denmark for 59 years (1588-1648), dreamed of making his kingdom a European power. The state in which he ruled was in fact a combination of three countries: the kingdoms of Denmark and Norway and the duchy of Schleswig. Good location and control of the Baltic straights were favorable for the country’s economic development, however at the same time they were the cause of potential conflicts – especially with Sweden, with which Denmark already had some old scores to settle. Against this background it is no surprise that the history of the reign of Christian IV is full of armed conflicts from which Denmark emerged seriously weakened. The beginning of the century did not forecast further problems: during the so called Kalmar War (1611-1613) Christian IV defeated Sweden, where during the war, the young Gustav II Adolph stated his reign. The decision to involve Denmark in the conflict that was to be called the Thirty Years War was fraught with consequences. The Danish ruler wanted to become a triumphant defender of Protestantism in Northern Germany and in 1626 he went on to fight against the catholic armies. However the Danish Rigsdag (parliament) did not support the martial initiative of the king who had to pay for recruitment of mercenary forces from his private treasury. “The Danish phase” of the war ended in a disaster. A series of defeats: Lutter am Bamberg in 1626, Heilligenhofen and Wolgast in 1627 led to the loss of the field army and moving the theatre of operations to Danish territory. The king lost Jutland and a number of fortresses protecting the kingdom’s border. In May 1629 Christian IV was forced to sign a peace treaty in Lübeck – despite regaining the lost territories his prestige was substantially damaged.
For more than ten years Denmark stayed away from the war that raged in Europe. Christian IV tried to mediate a peace between the Holy Roman Empire and Sweden, however his inept attempts at supporting the catholic side against the Swedes led to another catastrophe. The Swedish chancellor Oxenstierna, de facto the head of the state after Gustav II Adolph’s death, decided to attack Denmark and deprive it of any means of further involvement in the war. The Swedish-Danish conflict in the period from 1643 to 1645 went down in history as the Torstensson War, from the name of the field marshal leading the Swedish army. Within merely a month the Swedes conquered the whole of Jutland breaking any opposition of the weak Danish army. Only the intervention of the Danish fleet prevented an invasion of the Danish isles. The king himself was wounded thirteen times and lost one eye while fighting in the battle of Kolberg Heide. In the meantime Norwegian forces led by Hannibal Sehested successfully defended Norway and conducted several raids into Swedish territories. Unfortunately the policy of Christian IV that led to exacerbation of relations with the United Provinces led to the final defeat of Denmark in this war. Dutch warships supported the Swedes and the joint fleets defeated the Danes in September of 1644. Christian IV was forced to sign a peace treaty in Brömsebro on 13 August 1645. This time the price of peace was huge. The Swedes took Norwegian provinces of Jämtland,Härjedalen, Idre and Särna, as well as Danish islands of Gotlanc and Øsel. In addition they took over the Danish province of Halland for 30 years. What is worse Swedish ships and warships were exempt from paying duty in the Danish straits. Torstensson War also led Christian IV himself to bankruptcy as he used all his financial reserves to pay for the army and equip ships.
Frederic III took the throne after his father’s death in 1648. His task was not an easy one – he became the ruler of an indebted country the political significance of which fell into decline. One should also remember about the changes on the map of Europe after the Thirty Years War and how Sweden’s position changed. Frederic III focused on changes in state administration, starting the process which in 1660 was to introduce absolutism in Denmark. He was gradually rebuilding good relations with England and the United Provinces, thanks to which he ended a peculiar political isolation of Denmark on the international stage.
Denmark view the Swedish attack on the Polish-Lithuanian Commonwealth in 1655 with concern. The Danes remembered the treacherous attack of 1643 and voices that Denmark could be the next objective of Carl X Gustav’s offensive were heard throughout the country. Gradually as the situation in Poland changed in 1656 voices encouraging an attack against Sweden could be heard. It was believed that while the main Swedish forces were engaged in a far away theatre of operations the Danish army will be able to retake all territories lost in 1645 as well as occupy Swedish held Bremen. The worsening situation of the Swedes and promise of support given by the emperor Leopold I eventually turned the scales. On 1 June 1657 a Danish herald delivered an official declaration of war to Stockholm. There main Danish armies struck against Swedish-held territories: forces from Scania were to retake Halland, forces from Schleswig were to capture Bremen and Holstein, and Norwegian units were to take the provinces lost in 1645. However Danish generals did not expect that the veteran army of Carl X Gustav was already preparing to leave Poland and counterattack into Holstein. At the end of July 1657 the Swedish king’s army, after a forced march through Pomerania, attacked the Danes. Surprised, poorly commanded and not expecting such resistance soldiers of Frederick III posed only a symbolic resistance. Already at the beginning of September the Swedes entered Jutland. In the meantime operations in Halland were ineffective, only Norwegian forces achieved some success. In late autumn of 1657 it seemed that the war reached a stalemate. The Danish fleet, rebuilt after the defeat of 1644 made it impossible for the Swedes to attack the islands; operations in other theatres of war practically came to a standstill. However the weather came to the aid of Carl X Gustav: his army used the low temperatures that made the straits freeze and quickly marched against Copenhagen. The surprised Danes capitulated without a fight and on 26 February 1658 signed a disgraceful treaty of Roskilde. They lost more provinces: Scanias, Blekinge, Halland (this time as a permanent Swedish conquest) and Bohuslän, as well as the island of Bornholm. Also they were to pay for the maintenance of Carl X Gustav’s forces stationing in Denmark and send a contingent of several thousand men to support the Swedish army fighting in Poland.
However the peace was not to last for long. The Swedish king decided to break Denmark once and for all and in August 1658 struck once more. Europe was completely stunned by the shocking attack. One by one the Danish fortresses fell to Swedish assaults and only Copenhagen – supported by the Dutch fleet – stood against the invaders. Groups of partisans called the Snapphanar operated in the Swedish rear areas and there was a peasant revolt in Norwegian provinces occupied by the Swedes. More importantly the allied Brandenburg, Imperial and Polish forces came to Denmark’s aid. Their support was essential in retaking the Danish islands from the Swedes. Death of Carl X Gustav in February 1660 also had a significant influence on the ending of war. English, French and Dutch diplomats led to the signing of the Danish-Swedish peace treaty in Copenhagen on 6 June 1660. Denmark regained Trondheim and Bornholm but other Swedish gains of 1658 were left in their hands. Denmark was defeated and humiliated while loosing full control over the Baltic straits.
Christian IV conducted several reforms of the military system in Denmark (to a lesser degree in Norway), trying to base the army on national enlisted forces. The introduction of udskrivning in early 1620’s was the most important of them. It was a system of enlistment and financing of Danish recruits which lasted in an unchanged form until the end of the 17th century. It provided a basis for the national army, where enlisted men, not volunteers as before, served for 3 years in infantry and were trained by professional officers. In case of a serious danger it was possible to use opbud, that is forced recruitment of 1 out of every 5 peasants. However this was a desperate measure which was used only in 1627 in the face of a catholic invasion on Jutland. Cavalry was formed on the basis of rostjeneste, that is permanent mounted service of nobility and clergy (in fact the formation comprised of substitute peasants). Permanent mercenary units were also kept in service as fortress garrisons. Strong artillery was located in numerous arsenals. Denmark had large quantities of weapons and equipment which in case of a conflict could be used to arm the newly recruited units. Strong fleet, tasked with the protection of the Baltic straits played a very important role due to the geographic location of the country.
In general it may be assumed that the Danish soldier performed much better in defensive than in offensive actions – this was proved both by the war of 1657-58 and of 1658-60. Danes were able to fiercely defend Copenhagen in 1658 and inflict heavy losses on the assaulting Swedes. The enthusiasm that accompanied the declaration of war against Sweden in 1657 diminished quickly when the Danes faced Carl X Gustav’s veterans. Lack of flexibility was a serious problem of Danish commanders who lost too much time on fruitless councils while at the same time neglected the basic logistical needs of their forces – and this in turn resulted in low morale of their soldiers. Operations on the Norwegian-Swedish border were a commendable exception; there the energetic Iver Krabbe achieved some success against the Swedes.
The fact that the Danes had problems with the realization of mobilization plans that were prepared for several years also reflect badly on them. In 1652 field marshal Andres Bille developed a plan for the expansion of the Danish-Norwegian army in case of war. According to his assumptions the Danish army was to include 10 000 infantry and 5000 cavalry (in both cases national units), and the Norwegian army 9000 infantry and 1000 cavalry (also national units). When in 1657 frantic preparations for war begun, it turned out that both countries (especially Denmark) are unable to mobilize such a number of recruits. This caused additional burden to the state treasury – which was already seriously indebted – as numerous mercenaries had to be recruited. In contrast to his father, Frederick III had big problems with solvency, this influenced the recruitment capabilities and regular pay. Despite all these problems it was possible to field an army of 40 to 50 000 soldiers in October 1657 – in comparison in 1655 the whole Danish-Norwegian army numbered 20 000 men. After the truce in Roskilde the army was decreased to about 20 000 men, this number was achieved in summer of 1658. In the face of a new Swedish attack in 1658 it was possible to recruit another 10 000 men, however Denmark would not be able to stop the invader without the support of the Imperial-Brandenburg-Polish coalition.